Salmonella and Campylobacter reduction and quality characteristics of poultry carcasses treated with various antimicrobials in a post-chill immersion tank.

Innovations in poultry processing include implementation of antimicrobials in post-chill decontamination tanks. In this study, a total of 160 broiler carcasses were analyzed to evaluate the efficacy of five post-chill water treatments consisting of 0.004% (40ppm) total chlorine, 0.04% (400ppm) or 0.1% (1000ppm) peracetic acid (PAA), and 0.1% (1000ppm) or 0.5% (5000ppm) lysozyme against Salmonella and Campylobacter spp. In addition, sensory analysis was performed to evaluate any associated effects of the antimicrobials on quality attributes of chicken breast meat. Treatment with 0.04% and 0.1% PAA was most effective (P≤0.05) in reducing populations of Salmonella and Campylobacter as compared to the chlorine treatment at 0.004% and lysozyme treatments at 0.1% and 0.5%, as well as the water treatment and the positive control. Treatment with the various antimicrobials was not found to have negative (P≤0.05) impacts on sensory attributes. Results from this study suggest that utilizing PAA as an antimicrobial in a post-chill immersion tank is an effective application for reducing Salmonella and Campylobacter on carcasses while maintaining product quality.

Serum ferritin: does it differ from tissue ferritin?

Serum ferritin isolated from the horse was structurally compared with horse spleen ferritin and was found to differ markedly in molecular weight, iron content, carbohydrate, subunit size and amino acid sequence. The results are summarized and initial results obtained with candidate clones of pieces of two serum ferritin subunits are described.

Phylogenetic analysis of the aminoacyl-tRNA synthetases.

Numerous aminoacyl-tRNA synthetase sequences have been aligned by computer and phylogenetic trees constructed from them for the two classes of these enzymes. Branching orders based on a consensus of these trees have been proposed for the two groups. Although the order of appearance can be rationalized to fit many different scenarios having to do with the genetic code, the invention of a system for translating nucleic acid sequences into polypeptide chains must have predated the existence of these proteins. In the past, a variety of schemes has been proposed for matching amino acids and tRNAs. Most of these have invoked direct recognition of one by the other, whether or not the anticodon was involved. Often ignored is the possibility of a nonprotein (presumably RNA) matchmaker for bringing the two into conjunction. If such had been the case, then the contemporary aminoacyl-tRNA synthetases could have entered the system gradually, each specific type replacing its matchmaking RNA counterpart in turn. A simple displacement scheme of this sort accommodates the existence of two different families of these enzymes, the second being introduced well before the first had undergone sufficient genetic duplications to specify the full gamut of amino acids. Such a scheme is also consistent with similar amino acids often, but not always, being the substrates of enzymes with the most similar amino acid sequences.

Photoaffinity labeling of the primary fibrin polymerization site: isolation and characterization of a labeled cyanogen bromide fragment corresponding to gamma-chain residues 337-379.

Human fibrinogen and the plasmin-generated fibrinogen fragment D were photoaffinity labeled specifically with the peptide [14C]Gly-Pro-Arg-N(4-azido-2-nitrophenyl)Lys amide. In the case of fibrinogen, greater than 85% of the incorporated radioactivity was found in the gamma chain. Similarly, when fragment D (Mr, 90,000) was labeled with the same derivatized peptide, virtually all the radioactivity was found in the gamma-chain portion. The labeled fragment D was treated with CNBr and an initial purification was achieved by two gel-filtration steps. The labeled material was purified further by HPLC and was also compared with CNBr digests of unlabeled material. Amino acid analysis and gas-phase sequencing showed the labeled fragment to be gamma-chain residues 337-379.

A 9.6 S protein is the third calcium-insoluble component of the sea urchin hyaline layer.

A third major, calcium-insoluble component of the sea urchin (Strongylocentrotus purpuratus) hyaline layer has been purified and physically characterized. In the absence of divalent cations, the native, soluble protein has a sedimentation coefficient of 9.6 S and a molecular weight of 4.5 +/- 0.1 x 10(5). These data indicate that this large protein assumes an elongated, nonspherical conformation in solution. Its sedimentation behavior and its mobility on nondenaturing electrophoretic gels distinguish the 9.6 S protein from the 11.6 S and 6.4 S hyalin proteins we have previously characterized. That the 6.4 S, 9.6 S, and 11.6 S proteins are the major calcium-insoluble structural components of the hyaline layer is supported by the fact that we have found them in a variety of hyalin protein fractions prepared by a number of standard approaches. All three proteins are precipitated by calcium ions, thus fitting the operational definition of hyalin. Evidence is presented that the 11.6 S protein may overlie the 9.6 S protein in the hyaline layer.

Evolution and relatedness in two aminoacyl-tRNA synthetase families.

Sequence segments of about 140 amino acids in length, each containing a selected consensus region, were used in alignments of the aminoacyl-tRNA synthetases with the aim of discerning their evolutionary relationships. In all cases tested, enzymes specific for the same amino acid from a variety of organisms grouped together, reinforcing the supposition that the aminoacyl-tRNA synthetases are very ancient enzymes that evolved to include the full complement of 20 amino acids long before the divergence leading to prokaryotes and eukaryotes. The enzymes are divided into two mutually exclusive groups that appear to have evolved from independent roots. Group I, for which two sequence segments were analyzed, contains the enzymes specific for glutamic acid, glutamine, tryptophan, tyrosine, valine, leucine, isoleucine, methionine, and arginine. Group II enzymes include those activating threonine, proline, serine, lysine, aspartic acid, asparagine, histidine, alanine, glycine, and phenylalanine. Both groups contain a spectrum of amino acid types, suggesting the possibility that each could have once supported an independent system for protein synthesis. Within each group, enzymes specific for chemically similar amino acids tend to cluster together, indicating that a major theme of synthetase evolution involved the adaptation of binding sites to accommodate related amino acids with subsequent specialization to a single amino acid. In a few cases, however, synthetases activating dissimilar amino acids are grouped together.

Purification, physicochemical characterization, and immunohistochemical localization of a major 11.7 S glycoprotein from the jelly coats of the anuran Lepidobatrachus laevis.

Embryos of the frog Lepidobatrachus laevis are encased by a fertilization envelope and two jelly layers, termed J1 (innermost) and J2 (outermost). From preparations of total jelly solubilized from cleavage-stage embryos by a solution of alkaline beta-mercaptoethanol we have purified one jelly coat glycoprotein to homogeneity via FPLC gel permeation chromatography on Superose 6H. The purified glycoprotein was 94% protein and 6% carbohydrate, had an s0(20),w of 11.7 S, with a molecular weight of 245,000 measured by sedimentation equilibrium and 263,000 by gel permeation chromatography. SDS-PAGE revealed that the glycoprotein is composed of a single subunit near 29,700 molecular weight; thus we propose that eight of these subunits comprise the native molecule. Amino acid analysis of the glycoprotein indicated a high content of Glx + Asx (32.4 mole%), a low content of basic amino acids (Arg + Lys = 12.2 mole%), and a single cysteine residue per subunit. The N-terminal amino acid was threonine and the sequence of the first twenty amino acids was determined. Monospecific antisera to the glycoprotein were prepared in rabbits and were used to immunohistochemically localize the glycoprotein throughout the matrix of both jelly layers. Antiserum against the glycoprotein had virtually no effect on the fertilizability of jellied eggs in vitro; thus we hypothesize that the glycoprotein fulfills a structural role in both jelly layers.

Heart tissue contains small and large aggregates of ferritin subunits.

Ferritin purified from horse heart and applied to nondenaturing polyacrylamide gel electrophoresis migrated as a single band that stained for both iron and protein. This ferritin contained almost equal amounts of fast- and slow-sedimenting components of 58 S and 3-7 S, which could be separated on sucrose density gradients. Iron removal reduced the sedimentation coefficient of the fast-sedimenting ferritin to 18 S, and sedimentation equilibrium gave a molecular weight 650,000, with some preparations containing ferritin of 500,000 molecular weight as well. Sedimentation rates of the 3 S and 7 S ferritins were not affected by iron removal, and sedimentation equilibrium data were consistent with Mr's 40,000 and 180,000, respectively. Preparations of ferritin extracted from horse spleen contained only 67 S (holo) or 16 S (apo) ferritin and no slow-sedimenting species. When examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, all of the ferritins contained the usual H and L subunits (23 and 20 kDa, respectively), but the slow-sedimenting (3 S and 7 S) heart apoferritins also contained appreciable quantities (ca 25%) of three larger subunits of 42, 55, and 65 kDa. All the subunits reacted positively in Western blots to polyclonal antibodies made against specially purified large heart or spleen ferritins containing only 20- and 23-kDa subunits. Similar results were obtained for ferritins from rat heart. The results indicate that mammalian heart tissue is peculiar not just in having an abnormally large iron-rich ferritin but also in having iron-poor ferritins of much lower molecular weight, partly composed of larger subunits.

Dissociation of ferritins.

Apoferritins prepared from horse spleen and heart and rat heart and liver were dissociated by treatment with acetic acid (pH 1.3-3.0). Sedimentation velocity studies showed that apoferritins of spleen and liver (16-17 S) and heart (18-19 S) dissociated into material sedimenting near 3.2 S. Sedimentation equilibrium measurements determined that most of the material had a molecular weight of 38,000-43,000, corresponding to subunit dimers. Failure to dissociate into subunit monomers was confirmed by gel chromatography on Sephadex G-75 and G-150. With the exception of boiling in sodium dodecyl sulfate, further treatments with 0.1-0.4 M KCl, NaCl, 4-9 M urea, 0.01-0.5 M KSCN, 0.1-0.5% Triton X-100, 5-52% dimethylsulfoxide, 10% ethylene glycol, or 0.1% trifluoroacetic acid all failed to cause dissociation into individual subunits, as did exposure to 6 M guanidine-HCl or formic acid, or prior succinylation and/or nitration of the protein. Reassociation occurred between pH 4 and 7 but was not aided by the addition of Fe(II) or reducing agents. It is concluded that ferritins readily dissociate to subunit dimer units and that further dissociation does not occur without full denaturation of the protein.

A calcium-insoluble 6.4 S protein derived from sea urchin cortical granule exudate.

A major protein component of the sea urchin, Strongylocentrotus purpuratus, cortical granule exudate has been purified and characterized. In the absence of divalent cations, the native, soluble protein has a sedimentation coefficient at infinite dilution of 6.4 S and a molecular weight from sedimentation equilibrium measurements of 2.8 +/- 0.3 X 10(5). These and other data indicate that the protein assumes an elongated, rod-like structure in solution. The protein is greater than 95% homogeneous as judged by agarose- and sodium dodecyl sulfate-gel electrophoresis. In the latter experiments, the protein shows a relative molecular weight of 1.8 X 10(5) and is clearly distinct from the 11.6 S protein described earlier which shows two bands corresponding to 3.2 X 10(5) and 2.1 X 10(5). The 6.4 S protein is the major protein of the calcium-insoluble fraction of cortical granule exudate and contributes to the formation of the extracellular investments of the sea urchin embryo. Using a light-scattering assay, we show that the purified protein retains the ability to aggregate in the presence of divalent cations mirroring its assembly in vivo. Calcium ion alone is able to initiate this reaction and the rate of precipitation increases with calcium concentration. Magnesium alone is ineffective in this regard but, in combination, the two ions act synergistically. Strontium and barium can substitute for calcium, but higher concentrations of the former cations are required to produce an equivalent effect.

Glycyl-tRNA synthetase of Escherichia coli: immunological homology with phenylalanyl-tRNA synthetase.

Antibodies to Escherichia coli glycyl-tRNA synthetase (GlyRS) cross-react extensively with E. coli phenylalanyl-tRNA synthetase (PheRS). These data indicate that structural homology exists between these two enzymes, the only two aminoacyl-tRNA synthetases in E. coli having an alpha 2 beta 2 subunit structure. Although only limited similarities are found in the protein sequences deduced from their known gene sequences, the presence of common epitopes in GlyRS and PheRS adds to a rather long list of physical and chemical similarities between those proteins. In addition, antibodies directed at the alpha- and beta-subunits of GlyRS inhibit both GlyRS and PheRS in the same relative manner, indicating that the function as well as the structure of subunits is similar in each enzyme. In contrast, GlyRS antibodies did not cross-react with a number of other aminoacyl-tRNA synthetase activities from E. coli, yeast, or Bacillus.

Resolution and characterization of a major protein of the sea urchin hyaline layer.

A major protein component of the gel-like, embryonic hyaline layer of Strongylocentrotus purpuratus has been purified and characterized. The protein retains the ability to form an insoluble gel in the presence of specific divalent cations, a property characteristic of the hyaline material. Using a light scattering assay developed to measure the initial rate of hyalin gelation, we have been able to show that calcium alone is capable of initiating this reaction but that calcium and magnesium are synergistic in their effect. In the absence of divalent cations, the major hyalin protein has a molecular weight of 9.2 +/- 0.5 X 10(5) and a sedimentation coefficient of 11.6 S; these and other data indicate that the protein assumes a very elongated, rod-like structure in solution. Smaller amounts of two additional proteins, 8.8 and 6.5 S, are present in the hyalin fraction when the jelly coat and vitelline layer are subjected to a more stringent acid treatment early in the isolation procedure.

The beta subunit of E. coli glycyl-tRNA synthetase plays a major role in tRNA recognition.

The contributions made by the alpha and beta subunits of E. coli glycyl-tRNA synthetase to the recognition of tRNA have been investigated via binding and immunological methods. Using the nitrocellulose filter assay, we have shown that isolated beta subunit, but not the alpha subunit, binds [14C]glycyl-tRNA with an affinity comparable to that of the native enzyme. Further, the data indicate that the beta subunit possesses one binding site for glycyl-tRNA while the native or reconstituted enzyme (alpha 2 beta 2) has two sites. Rabbit antibodies directed at the beta subunit or the holoenzyme inhibit efficiently the ability of the enzyme to aminoacylate tRNA while alpha-subunit antibodies have a smaller effect. Since none of the antisera have an appreciable effect on the ATP-PPi exchange activity of the enzyme under these conditions, the beta-subunit (and holoenzyme) antisera evidently interfere with productive tRNA binding. Taken together, the data indicate that the larger, beta subunit of glycyl-tRNA synthetase plays a major role in tRNA recognition.

The size and shape of heart and muscle ferritins analyzed by sedimentation, gel filtration, and electrophoresis.

We have compared the size and shape of ferritins from human heart, rat heart, and skeletal muscle with those of rat liver and horse spleen ferritins, using sedimentation and gel filtration techniques. The electrophoretically "fast" form of heart ferritin was partially separated from both the "slow" heart form and from rat liver ferritin by gel filtration (Stokes radii 72 A versus 69 and 68.5 A). Sedimentation velocity after iron removal showed an 18.5 S boundary even for mixtures of the two heart species, versus 17.3 S for rat liver and horse spleen apoferritins. Holoferritins gave a broad boundary, with coefficients from 66-80 S depending on iron content. Variable amounts of disaggregated ferritin (2.6 S) were also present in the heart ferritin preparations. Removal of iron significantly increased the electrophoretic migration of the fast but not the slow heart ferritin species. By sedimentation equilibrium, the molecular weights of all apoferritins save the fast heart form were about 490,000; that for the latter was near 750,000. Since electrophoresis revealed no major differences in subunit size, it is concluded that the larger, more asymmetric form of muscle ferritin contains 34 to 38 rather than 24 subunits.

Cooperative interactions in hybrids of aspartate transcarbamylase containing succinylated regulatory polypeptide chains.

Succinylated derivatives of the regulatory subunit of aspartate transcarbamylase of Escherichia coli were prepared by treating the intact enzyme with succinic anhydride followed by dissociation of the modified protein into catalytic and regulatory subunits which were separated by ion exchange chromatography. The succinylated regulatory subunits were used in hybridization experiments with native subunits to study the organization of the six regulatory polypeptide chains in the intact enzyme. Rapid mixing of succinylated and native regulatory subunits with native catalytic subunits yielded a four-membered hybrid set of reconstituted enzyme-like molecules; hence, the assembly process involves three regulatory combining units and the six regulatory polypeptide chains in the intact enzyme must be arranged as three dimeric subunits. When the modified and native regulatory subunits were incubated together for only brief periods (less than 1 min) followed by the addition of catalytic subunits, the resulting hybrid set was complex with no resolution of discrete species. Apparently the isolated regulatory dimers dissociate readily and reversibly into single polypeptide chains due to relatively weak intra-subunit bonding domains. In contrast, after reconstitution of enzyme-like molecules, the incorporated succinylated regulatory subunits did not exchange with free subunits. Enzyme-like molecules containing three extensively succinylated regulatory subunits show reduced binding of the inhibitor, CTP, and lack both the homotropic and heterotropic effects characteristic of native aspartate transcarbamylase. Preparations containing only slightly succinylated regulatory subunits showed only little inhibition by CTP and considerable cooperativity. The decrease in homotropic effects in these reconstituted molecules correlated with the reduction in the succinate-promoted change in the sedimentation coefficient. Reconstituted enzyme-like molecules containing regulatory subunits which had been extensively succinylated in the presence of CTP retained their binding capacity even though they were only slightly inhibited by CTP and exhibited reduced cooperativity. Hybrid molecules containing both native and succinylated regulatory subunits also possessed reduced allosteric behavior.

Aspartate transcarbamoylase molecules lacking one regulatory subunit.

Reconstitution of aspartate transcarbamoylase (EC 2.1.3.2) from dilute solutions of the isolated regulatory and catalytic subunits, with the latter in large excess, led to the formation of appreciable amounts of a second, stable component in addition to the reconstituted enzyme. The purified component, designated r(4)c(6), was found to have a molecular weight about 3 x 10(4) less than that of the native enzyme, and it combined with isolated regulatory subunit to form aspartate transcarbamoylase. It also combined with one succinylated regulatory subunit to form a hybrid species that was identified electrophoretically. These findings indicate that r(4)c(6) differs from the native enzyme in that only two (rather than three) regulatory subunits participate in "crosslinking" the two catalytic trimers. The "incomplete" enzyme, r(4)c(6), exhibits the characteristic sigmoidal saturation behavior and CTP inhibition of aspartate transcarbamoylase; however these allosteric effects are reduced in extent by about one-third in comparison to the native enzyme and free catalytic subunits. The complex, which may be an intermediate in the assembly and dissociation of the native enzyme, is useful in assessing the role of the various bonding domains responsible for the stability and regulatory properties of the native enzyme.