COVID-19 Effects on Income and Dental Visits: A Cross-sectional Study.

OBJECTIVES: In April 2020, the Japanese government declared a state of emergency owing to the outbreak of the novel coronavirus disease (COVID-19) pandemic, which resulted in reduced workforce and job losses. Furthermore, income is one of the most consistent predictors of dental visits. Therefore, this study examined the association between income changes and dental clinic visits during the COVID-19 state of emergency in Japan. METHODS: An online, self-reported cross-sectional survey about health activities including dental visits during the first COVID-19 state of emergency was conducted in Osaka, Japan (June 23 to July 12, 2020). Among participants with toothaches, the assessment for the association between "refrained from visiting a dentist despite wanting treatment for toothache during the state of emergency (refrained treatment)" and income changes before and after the state of emergency using a multivariate Poisson regression model adjusted for sex, age, self-rated health, frequency of regular dental visits, and employment status. RESULTS: Among 27,575 participants, 3,895 (14.1%) had toothaches, and 1,906 (6.9%) reported refrained treatment. Among people with decreased income (n = 8,152, 29.6% of overall participants), the proportions of the refrained treatment group were 8.0% (income decreased by 1%-49%), 9.9% (50%-99% decreased), and 9.1% (100% decreased). Among participants with toothache, after adjusting for all variables, compared with participants with no income change, we observed significantly higher prevalence ratios (PRs) for refrained treatment in those who experienced a decreased income owing to COVID-19 (1%-49% decrease: PR = 1.08; 95% confidence interval [CI], 1.005-1.17; 50%-99% decrease: PR = 1.18; 95% CI, 1.06-1.32; 100% decrease: PR = 1.18; 95% CI, 1.04-1.33). CONCLUSION: Decreased income was associated with refrained dental treatment during the COVID-19 state of emergency in Osaka, Japan. The economic damage related to the COVID-19 pandemic could lead to oral health inequalities. KNOWLEDGE TRANSFER STATEMENT: Our study found that individuals with decreased income owing to COVID-19 before and after the state of emergency showed significantly higher prevalence ratios for refraining from visiting a dentist despite wanting treatment for toothache. We believe that our study makes a significant contribution because it provides novel, basic data that economic damages related to the COVID-19 pandemic might expand to oral health inequalities.

Identification of a rat 30-kDa protein recognized by the antibodies to a recombinant rat cutaneous fatty acid-binding protein as a 14-3-3 protein.

Immunoblot analysis with polyclonal antibodies raised against a recombinant rat cutaneous fatty acid-binding protein revealed a 30-kDa protein other than the 15-kDa fatty acid-binding protein in rat skin cytosol. This protein was present in a number of rat organs and in mouse 3T3 L1 cells. The amino acid sequences of the enzymatic peptides of the 30-kDa protein extracted from SDS-PAGE gels suggested that it was a mixture of the subunits of the eukaryotic signaling molecule, 14-3-3 protein. Glutathione S-transferase fusion proteins of 14-3-3 protein subunits were examined for cross-reaction by Western blotting, and the epsilon-subunit alone was found to be immunoreactive, so far as tested. It is likely that the 30-kDa protein detected in the rat tissues by the antibodies is the 14-3-3 protein epsilon-subunit. Although there is no apparent sequence similarity between the fatty acid-binding protein and the 14-3-3 protein subunit, they appear to share a common structural element recognized by the antibodies. Since 14-3-3 proteins and fatty acid-binding proteins are known to interact with a wide variety of cellular proteins, the presence of a common local structure might mutually modulate such interactions.

Hepatic fatty acid-binding proteins of a teleost, Lateolabrax japonicus. The primary structures and location of a disulfide bond.

Two fatty acid-binding proteins (FABP), FABP-1 and FABP-2, were purified from the liver cytosol of the teleost, Lateolabrax japonicus (Japan sea bass), and characterized. The complete primary structure of FABP-2 was determined by protein analysis to be the following: MDFSGTWQVY AQENYEEFLR AMELPADVIK MAKDIKPITE IKQSGNDFVV TSKTPGKTVT NSFTIGKEAD ITTMDGKKIR CVVNLEGGKL VCNTGKFCHI QELRGGEMVE TLTMGSTTLI RKSKKM. Partial peptide sequences of FABP-1 were also determined. Phylogenetic analysis indicates that FABP-2 is a homologue of mammalian hepatic FABP, whereas FABP-1 is most similar to the members of mammalian cardiac FABP subfamily. L. japonicus FABP-2 contains three cysteine residues, and a disulfide bond is identified between Cys-81 and Cys-92. A theoretical model of FABP-2 generated by a homology modeling method indicates close proximity of the two cysteine residues in the three-dimensional structure. This is a rather rare case of cytosolic protein having a disulfide bond under the normally reducing conditions of the cytosol, though the presence or absence of disulfide bonds does not seem to affect the ligand-binding ability.

Disulfide bonds in rat cutaneous fatty acid-binding protein.

Unlike other fatty acid-binding proteins, cutaneous (epidermal) fatty acid-binding proteins contain a large number of cysteine residues. The status of the five cysteine residues in rat cutaneous fatty acid-binding protein was examined by chemical and mass-spectrometric analyses. Two disulfide bonds were identified, between Cys-67 and Cys-87, and between Cys-120 and Cys-127, though extent of formation of the first disulfide bond was rather low in another preparation. Cys-43 was free cysteine. Homology modeling study of the protein indicated the close proximity of the sulfur atoms of these cysteine pairs, supporting the presence of the disulfide bonds. These disulfide bonds appear not to be directly involved in fatty acid-binding activity, because a recombinant rat protein expressed in Escherichia coli in which all five cysteines are fully reduced showed fatty acid-binding activity as examined by displacement of a fluorescent fatty acid analog by long-chain fatty acids. However, the fact that the evolutionarily distant shark liver fatty acid-binding protein also has a disulfide bond corresponding to the one between Cys-120 and Cys-127, and that fatty acid-binding proteins play multiple roles suggests that some functions of cutaneous fatty acid-binding protein might be regulated by the cellular redox state through formation and reduction of disulfide bonds. Although we cannot completely exclude the possibility of oxidation during preparation and analysis, it is remarkable that a protein in cytosol under normally reducing conditions appears to contain disulfide bonds.

Processing pathway deduced from the structures of N-glycans in Carica papaya.

A processing The processing pathway of N-glycans in Carica papaya was deduced from the structures of N-glycans. The N-glycans were liberated by hydrazinolysis followed by N-acetylation. Their reducing-end sugar residues were tagged with 2-aminopyridine and the pyridylamino (PA-) sugar chains thus obtained were purified by HPLC. Eleven PA-sugar chains were found, and their structures were analyzed by two-dimensional sugar mapping combined with partial acid hydrolysis and exoglycosidase digestion. The structures of the N-glycans were of the highmannose types with xylose and fucose; however, among them two new N-glycans, Manalpha1-6(Manalpha1-3)Manalpha1-6(Xylbeta1-2)+ ++Manbeta1-4GlcNAcbeta1- 4(Fucalpha1-3)GlcNAc and Manalpha1-3Manalpha1-6(Xylbeta1-2)Manbeta1-4G lcNAcbeta1-4(Fucalpha1-3 )GlcNAc, were found. Judging from these structures together with Manalpha1-6(Manalpha1-3)Manalpha1-6(Manalpha1-3) (Xylbeta1-2)Manbeta1- 4GlcNAcbeta1-4(Fucalpha1-3)GlcNAc reported previously [Shimazaki, A., Makino, Y., Omichi, K., Odani, S., and Hase, S. (1999) J. Biochem. 125, 560- 565], a processing pathway for N-glycans in C. papaya is inferred in which the activity of Golgi alpha-mannosidase II is incomplete.

The coxsackievirus-adenovirus receptor protein as a cell adhesion molecule in the developing mouse brain.

In an attempt to elucidate the molecular mechanisms underlying neuro-network formation in the developing brain, we analyzed 130 proteolytic cleavage peptides of membrane proteins purified from newborn mouse brains. We describe here the characterization of a membrane protein with an apparent molecular mass of 46 kDa, a member of the immunoglobulin superfamily of which the cDNA sequence was recently reported, encoding the mouse homologue of the human coxsackievirus and adenovirus receptor (mCAR). Western and Northern blot analyses demonstrated the abundant expression of mCAR in the mouse brain, the highest level being observed in the newborn mouse brain, and its expression was detected in embryos as early as at 10. 5 days post-coitus (dpc), but decreased rapidly after birth. On in situ hybridization, mCAR mRNA expression was observed throughout the newborn mouse brain. In primary neurons from the hippocampi of mouse embryos the expression of mCAR was observed throughout the cells including those in growth cones on immunohistochemistry. In order to determine whether or not mCAR is involved in cell adhesion, aggregation assays were carried out. C6 cells transfected with mCAR cDNA aggregated homophilically, which was inhibited by specific antibodies against the extracellular domain of mCAR. In addition to its action as a virus receptor, mCAR may function naturally as an adhesion molecule involved in neuro-network formation in the developing nervous system.

Homozygous deletions and point mutations of the Ikaros gene in gamma-ray-induced mouse thymic lymphomas.

Our previous genome-wide analysis of allelic loss for thymic lymphomas that were induced by gamma-irradiation in F1 hybrid mice between BALB/c and MSM strains suggested the centromeric region on chromosome 11 as a site harboring a tumor suppressor gene. Interestingly, to this region the mouse Ikaros gene was mapped which was postulated to participate in oncogenic process from the study of Ikaros knockout mice. Here we show fine allelic loss mapping in the vicinity of Ikaros in 191 lymphomas, indicating that the critical region of allelic loss was centered at the Ikaros locus. PCR analysis revealed that nine lymphomas failed to give PCR-amplification for either of two exon primer pairs, indicative of homozygous deletion. Six and five mutations were detected in the N-terminal zinc finger domain and the activation domain of Ikaros, respectively, and six of the eleven were frameshift or nonsense mutations that resulted in truncation of Ikaros protein. The results strongly suggest a direct role for Ikaros in development of mouse thymic lymphomas. This provides the experimental basis for further analysis of Ikaros mutations in human cancer.

Five different genes, Eif4a1, Cd68, Supl15h, Sox15 and Fxr2h, are clustered in a 40 kb region of mouse chromosome 11.

We characterized a region of the mouse genome disrupted by integration of a gene trap (GT) vector in ES cells. On 5' rapid amplification of cDNA ends analysis of the fusion transcripts containing the GT vector, we identified the eukaryotic protein synthesis initiation factor 4A1 gene (Eif4a1) as a promoter-trapped gene. Plasmid rescue was used to show that the other end of the integrated vector disrupted the murine homolog of the human fragile X mental retardation syndrome-related protein 2 gene (Fxr2h). Structural analysis of P1 clones, isolated from the wild-type mouse genome by PCR with Eif4a1-specific primers, indicated that the integration of the GT vector was accompanied by the deletion of about 35 kb of genomic DNA and that the disrupted region also included three genes, Cd68, Supl15h and Sox15, the latter two of which are transcribed in opposite directions with overlapping 3' ends. These five different genes at least, Eif4a1, Cd68, Supl15h, Sox15 and Fxr2h, are clustered in a 40 kb region. The chromosomal location of this region was mapped by means of interspecific backcross panel DNAs to the central part of mouse chromosome 11, exhibiting a known region of synteny with human chromosome 17.

Structural analysis of the amyloidogenic kappa Bence Jones protein (FUR).

Patients with systemic amyloidosis associated with multiple myeloma (AL-amyloidosis) exhibit immunoglobulin light chains and fragments which have been identified as amyloid protein. Since a relatively small proportion of patients with multiple myeloma develop AL-amyloidosis, comparison of the amino acid sequence of the amyloidogenic and non-amyloidogenic immunoglobulin light chains and the structural characterization of the amyloid proteins are required to understand the relationship between structure and amyloidogenicity. We determined the primary structure of a kappa I-type Bence Jones protein obtained from a patient (FUR) who had systemic AL-amyloidosis associated with multiple myeloma. We identified eight amino acid replacements unique to this patient among the amyloidogenic kappa I-light chains, and which are also rare among the known kappa type light chains of humans. Three of these substitutions were within the framework regions and may act to destabilize the structure to promote a putative amyloidogenic conformation. In contrast to light chain fragments in the urine, which were processed in the variable region, mass spectrometric analysis of the fibril proteins isolated from lingual amyloid deposits in this patient, revealed that they were all truncated within the constant region and corresponded to residues 1-125, 1-144, and 1-210. Inspection of the predicted three-dimensional model of this protein suggested that these fragments may be generated by a protease specific for the N-terminal sides of basic amino acids. These findings suggest that amino acid substitutions at highly conserved residues may convert non-amyloidogenic to amyloidogenic immunoglobulin light chain proteins.

The inhibitory properties and primary structure of a novel serine proteinase inhibitor from the fruiting body of the basidiomycete, Lentinus edodes.

A novel proteinase inhibitor, Lentinus proteinase inhibitor, has been purified from the fruiting bodies of the edible mushroom, Lentinus edodes, by buffer extraction and affinity chromatography on immobilized anhydrotrypsin. The protein simultaneously inhibits bovine beta-trypsin and alpha-chymotrypsin at independent sites, with apparent dissociation constants of 3.5 x 10(-10) M and 4 x 10(-8) M, respectively. The purified protein is eluted as two well-separated peaks on reversed-phase HPLC, one of which is inhibitory-active and the other inactive, and they are interconvertible under folding/unfolding conditions. Among the mammalian and microbial serine proteinases examined, including human enzymes of blood coagulation and fibrinolysis, activated factor XI was inhibited by the Lentinus proteinase inhibitor. Chemical modification studies suggest involvement of one or more arginine residues in the inhibition of trypsin. The complete primary structure composed of 142 amino acids with an acetylated N-terminus was determined by protein analysis. The theoretical molecular mass (15999.2) from the sequence is close to the experimental value of 15999.61 +/- 0.61 determined by mass spectrometry. Although there are no apparently homologous proteinase inhibitors in the protein database, there is a rather striking similarity to the propeptide segment of a microbial serine proteinase, as well as to the N-terminal region of the mature enzyme.

The amino acid sequence of a lamprey (Entosphenus japonicus) liver fatty acid-binding protein identified its close relationship to cardiac fatty acid-binding proteins of Mammalia.

Fatty acid-binding proteins (FABPs) constitute a large, tissue-specific multigene family in animals. While liver FABPs of Aves, Reptilia, and Amphibia are close homologs of mammalian liver FABPs, the shark liver protein belongs to the mammalian heart FABP subfamily. We purified an FABP from the liver of lamprey, Entosphenus japonicus, by gel filtration and anion-exchange chromatography. Amino acid sequences determined for lysyl endopeptidase peptides covered nearly the entire molecule except for N- and C-terminal short segments. Examination of the phylogenetic relationship from the sequence identified the lamprey liver protein as a member of mammalian heart-type FABPs. Since livers of bony fish contain both hepatic and cardiac FABPs, expression of the FABP gene in the vertebrate liver appears to change from the heart-type to liver-type within Pisciformes, with bony fish being in a transition stage. This may be related to the evolutionary and physiological divergence of liver function and lipid metabolism of these lower vertebrates.

A new sugar chain of the proteinase inhibitor from latex of Carica papaya.

The structure of a sugar chain of the proteinase inhibitor from the latex of Carica papaya was studied. Sugar chains liberated on hydrazinolysis were N-acetylated, and their reducing-end residues were tagged with 2-aminopyridine. One major sugar chain was detected on size-fractionation and reversed-phase HPLC analyses. The structure of the PA-sugar chain was determined by two-dimensional sugar mapping combined with sequential exoglycosidase digestion and partial acid hydrolysis, and by 750 MHz 1H-NMR spectroscopy. The structure found was Manalpha1-6(Manalpha1-3)Manalpha1-6(Manalpha1-3) (Xylbeta1-2)Manbeta1- 4GlcNAcbeta1-4(Fucalpha1-3)GlcNAc. This sugar chain represents a new plant-type sugar chain with five mannose residues.

Distinct regional distribution in the brain of messenger RNAs for the two isoforms of synaphin associated with the docking/fusion complex.

Synaphin is a 19,000 mol. wt cytosolic protein we first found to co-purify with the docking/fusion complex crucial to neurotransmitter release from presynaptic terminals. Two isoforms of synaphin (synaphins 1 and 2) (also called complexins II and I, respectively) exist in the rat brain. On density gradient centrifugation of a Triton X-100 extract of brain membranes, synaphin was found to be associated with the 7S complex that contains synaptotagmin, syntaxin, synaptosomal-associated protein of 25,000 mol. wt and vesicle-associated membrane protein. A smaller complex devoid of synaphins was also identified by immunoprecipitation with a monoclonal antibody against synaptosomal-associated protein of 25,000 mol. wt. Messenger RNAs for synaphins 1 and 2 were expressed predominantly in the brain. In situ hybridization using probes specific to synaphins 1 and 2 indicated that the distribution of their mRNAs was significantly different in brain regions such as olfactory bulb, hippocampus, cerebral cortex, piriform cortex, cerebellum, thalamus and facial nuclei. These results show synaphin as a component of the 7S complex and suggest different physiological implications for the two isoforms.

Characterization and primary structure of a fatty acid-binding protein and its isoforms from the liver of the Amphibia, Rana catesbeiana.

Fatty acid-binding protein (FABP) was purified from the liver of the Amphibia, Rana catesbeiana, by gel filtration and ion-exchange chromatography. The complete primary structure of the frog liver FABP was determined by protein analysis. Two isoforms, I and II, were separated by reversed phase HPLC, and found to differ by 10 atomic mass units as measured by ion-spray ionization mass spectrometry. A detailed analysis of enzymatic peptides revealed a single Pro (isoform I)/Ser (isoform II) replacement at position 16. It seems remarkable that a rather neutral point mutation results in the nearly complete separation of the two isoforms by reversed phase chromatography. Homology modeling suggests the location of this site on the first helix of the helix-turn-helix domain and the presence of a single thiol group of cysteine-91 at the inside of the ligand-binding cavity. Binding studies using a natural fluorescent fatty acid, cis-parinaric acid, showed a lower Kd value for the serine form and large enhancement of fluorescence intensity upon glutathione-thiolation at cysteine-91. Examination of phylogenetic relationships identified the frog liver protein as a mammalian liver type FABP, and suggested a change in the vertebrate liver FABP gene expression at the bony fish/cartilagenous fish boundary.

Purification, characterization and cDNA cloning of soluble carbonic anhydrase from Chlorella sorokiniana grown under ordinary air.

Soluble carbonic anhydrase (CA, EC 4.2.1.1) inducible by low levels of CO2 was purified from the unicellular green alga Chlorella sorokiniana grown at alkaline pH. The purified CA had a specific activity of 2,300 units (mg protein)-1. The molecular mass of the CA was found to be 100 kDa by non-dissociating (native)-polyacrylamide gel electrophoresis and 50 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The 50-kDa subunit was recognized by concanavalin A. These results suggest that the protein has a dimeric form with two 50-kDa subunits that are glycosylated in an asparagine-linked manner. The native CA was revealed by isoelectric focusing to be a very acidic protein with an isoelectric point of 4.2. About 60% of the CA activity was inhibited by 0.5 M NaCl. The enzyme was inactivated over 95% by preincubation with 50 mM dithiothreitol but not with 1 mM dithiothreitol. After partial amino acid sequence analysis, a cDNA clone of the CA was isolated and characterized. The cloned cDNA fragment encoded a 348-amino-acid polypeptide (36,709 Da) including an NH2-terminal hydrophobic signal peptide composed of 35 amino acids (3,725 Da). Conserved regions of sequences found in animal CAs, in the periplasmic (pCA) and the intracellular CAs of Chlamydomonas, and in the plasma-membrane-bound CA of Dunaliella (Dca) were also found in this Chlorella CA. The signal sequence was significantly homologous to the pCA and the Dca. The internal signal sequence between the large and the small subunits reported for pCA was not found in this Chlorella CA. The soluble CA of this alga was an alpha-type CA with salt-sensitive, periplasm-locating and acidic properties and very different from pCA and Dca with their salt-sensitive/neutral and salt-resistant/acidic properties, respectively.

Isolation and primary structure of a methionine- and cystine-rich seed protein of Cannabis sativa.

A 10-kDa protein was isolated from resting seeds of hemp (Cannabis sativa) by buffer extraction, gel filtration, ion-exchange chromatography, and reversed-phase high-pressure liquid chromatography. The protein did not inhibit bovine trypsin. It consisted of subunits composed of 27 and 61 residues and was held together by two disulfide bonds. The complete amino acid sequence was identified by protein analysis, and had 20 mole% of amino acids containing sulfur. The protein was most similar to a methionine-rich protein of Brazil nut (Bertholletia excelsa) and to Mabinlin IV, a sweetness-inducing protein of Capparis masaikai. The high methionine content and the absence of trypsin inhibitory activity suggested that the seed protein can be used to improve the nutritional quality of plant food-stuffs.

Cloning and expression of cDNA encoding rat liver 60-kDa lysophospholipase containing an asparaginase-like region and ankyrin repeat.

Mammalian tissues contain small form and large form lysophospholipases. Here we report the cloning, sequence, and expression of cDNA encoding the latter form of lysophospholipase using antibody raised against the enzyme purified from rat liver supernatant (Sugimoto, H., and Yamashita, S. (1994) J. Biol. Chem. 269, 6252-6258). The 2,539-base pair cDNA encoded 564 amino acid residues with a calculated Mr of 60,794. The amino-terminal two-thirds of the deduced amino acid sequence significantly resembled Escherichia coli asparaginase I with the putative asparaginase catalytic triad Thr-Asp-Lys and was followed by leucine zipper motif. The carboxyl-terminal region carried ankyrin repeat. When the cDNA was transfected into HEK293 cells, not only lysophospholipase activity but also asparaginase and platelet-activating factor acetylhydrolase activities were expressed. Reverse transcription-polymerase chain reaction revealed that the transcript occurred at high levels in liver and kidney but was hardly detectable in lung and heart from which large form lysophospholipases had been purified, suggesting the presence of multiple forms of large form lysophospholipase in mammalian tissues.

Bilirubin binding activity of cytokeratin 18 isolated from the porcine liver.

A porcine liver 40 kDa protein designated SBP40 isolated by affinity chromatography with agarose-linked spermine was identified as a porcine cytokeratin 18 on the basis of partial amino acid sequences of peptides derived by lysylendopeptidase digestion and by its reactivity with two commercially available preparations of monoclonal antibody. Immunohistochemistry revealed that SBP40 is localized at the hepatocyte membranes, preferentially in the bile canalicular area in accordance with the previously reported localization of cytokertain 18 in the murine liver. Affinity chromatography with agarose-linked bilirubin, a solubilization experiment of bilirubin from bilirubin-Sephadex G-10 complex, and gel-filtration of a mixture with bilirubin demonstrated that SBP40 or porcine cytokeratin 18 has binding affinity for bilirubin. These results suggest that cytokeratin 18 may play a role as a membrane reservoir in the event of transport and secretion of bile pigments in the liver.

Protective protein in the bovine lysosomal beta-galactosidase complex.

Cathepsin A [EC 3.4.16.1], so called protective protein, occurs as an enzyme complex with lysosomal beta-galactosidase [3.2.1.23] and is involved in the stable enzymic expression of lysosomal sialidase [3.2.1.18]. In this study we investigated the enzymatic properties of cathepsin A in the bovine beta-galactosidase complex and how it is involved in the molecular multiplicities of the beta-galactosidase and sialidase complexes. Bovine protective protein homologous to the human protein had a molecular weight of 48 kDa on SDS-PAGE and cathepsin A activity optimum around pH 6.0. It hydrolyzed dipeptide substrates composed of hydrophobic amino acids much faster than any other type of substrate tested. This specificity was found to be conserved from human to a non-mammal, chicken. Immunoprecipitation using an anti beta-galactosidase antibody demonstrated that cathepsin A is a component of both the sialidase and beta-galactosidase complexes. The over 700 kDa sialidase complex depolymerized by a brief incubation at pH 7.5 and the sialidase was inactivated irreversibly via formation of an enzyme active smaller species of sialidase. The 669 kDa beta-galactosidase complex dissociated reversibly into a 120 kDa beta-galactosidase and a 170 kDa cathepsin A, but the 120 kDa beta-galactosidase, free from the cathepsin A, formed a 260 kDa aggregate under the same conditions. Inactivation of cathepsin A by heat treatment did not affect its complex forming activity. The 170 kDa protective protein dissociated into a 50 kDa one at pH 7.5, which no longer formed the complex. These findings indicate that the 170 kDa protective protein could be the minimum unit required for in vitro reconstitution of the complex, and that its complex forming activity is carried in a heat-stable domain. Both beta-galactosidase and cathepsin A activities were labile under the dissociated condition, indicating that it physiologically stabilizes not only beta-galactosidase but also itself by forming the complex.

The presence of the 50-kDa subunit of dynactin complex in the nerve growth cone.

Membrane proteins in growth cone-enriched and growth cone-non-enriched fractions prepared from neonatal mouse brain were separated by lectin-affinity and ion exchange chromatographies, 2D-PAGE, and SDS-PAGE. Partial amino acid sequences of the proteins concentrated in the growth cone-enriched fraction were determined. We found that one such protein, gmp23-48k, corresponds to the 50-kDa subunit (p50) of the dynactin complex. An antibody raised against gmp23-48k strongly reacted with growth cones of differentiated neuronal precursor cells. Immunoblot analyses revealed that gmp23-48k was present both in membrane and in soluble fractions of neonatal brain. However, the amount of gmp23-48k in the membrane fraction greatly decreased in adult brain. These results suggest a special role of membrane-associated gmp23-48k/p50 in synapse formation during brain development.