Sequence analysis of the myosin regulatory light chain gene of the vestimentiferan Riftia pachyptila.

We have isolated and characterized a cDNA (DNA complementary to RNA) clone (Rf69) from the vestimentiferan Riftia pachyptila. The cDNA insert consists of 1169 base pairs. The aminoacid sequence deduced from the longest reading frame is 193 residues in length, and clearly characterized it as a myosin regulatory light chain (RLC). The RLC primary structure is described in relation to its function in muscle contraction. The comparison with other RLCs suggested that Riftia myosin is probably regulated through its RLC either by phosphorylation like the vertebrate smooth muscle myosins, and/or by Ca2+-binding like the mollusk myosins. Riftia RLC possesses a N-terminal extension lacking in all other species besides the earthworm Lumbricus terrestris. Aminoacid sequence comparisons with a number of RLCs from vertebrates and invertebrates revealed a relatively high identity score (64%) between Riftia RLC and the homologous gene from Lumbricus. The relationships between the members of the myosin RLCs were examined by two phylogenetic methods, i.e. distance matrix and maximum parsimony. The resulting trees depict the grouping of the RLCs according to their role in myosin activity regulation. In all trees, Riftia RLC groups with RLCs that depend on Ca2+-binding for myosin activity regulation.

Cell type-specific gene expression in the cell cycle of the dimorphic ciliate Eufolliculina uhligi.

The life cycle of the unicellular eukaryote Eufolliculina uhligi includes two structurally and physiologically different cell types: a motile swarmer that is arrested in the cell cycle, and a sessile cell (trophont) that feeds and reproduces. These two cell types offer an exceptionally favourable system for the isolation of genes involved in cell cycle regulation and cellular morphogenesis. Differential screening of a trophont cDNA library using a swarmer-subtracted, trophont-specific probe yielded eleven clones that represent trophont-specific transcripts and one clone that represents a swarmer-specific transcript. Sequence analysis showed that seven clones, including the only swarmer-specific one, represent unknown genes, whereas five clones could be identified by sequence comparisons. Two of the clones appear to encode proteins that are involved in the regulation of growth and metabolism. The deduced sequences of three clones resemble potential cell cycle regulators. Data are presented on a putative member of the calcium/calmodulin-dependent protein kinase family and on a TIP120-like sequence, which is the first such sequence to be described since the discovery of the rat TIP120 protein. Furthermore, a unique new sequence is presented, whose features suggest that it represents a protein that is involved in the regulation of cell division. It includes domains characteristic of two different protein families, cyclin-dependent kinases (CDKs) and cyclins, both of which are known to be cell cycle regulators. Based on our results we propose a model for cell cycle regulation in ciliated protozoa.

Novel gene expressed in spleen cells mediating acquired testosterone-resistant immunity to Plasmodium chabaudi malaria.

We report the identification of a novel mouse cDNA encoding IAP38, a putative plasma membrane protein of 38 kDa in splenic macrophages, B cells and T cells. The expression of iap38 is induced by blood-stage infections of Plasmodium chabaudi malaria and is testosterone-sensitive in non-immune mice. However, when mice have acquired testosterone-resistant immunity to P. chabaudi, there is an about 40-fold increase in the expression of iap38, which has then largely lost its responsiveness to infection and testosterone. The gene iap38 is suggested to be involved in imparting spleen cells the ability to mediate testosterone-resistant immunity to P. chabaudi malaria.

Nucleotide sequence of maize chloroplast rpS11 with conserved amino acid sequence between eukaryotes, bacteria and plastids.

Nucleotide sequence of a 721 base pair segment of maize chloroplast DNA, encoding the putative chloroplast ribosomal protein S11 at physical map position 33.1-33.5 Kbp, is described. A Shine-Dalgarno sequence and computer-derived stem-loop structures of dyad symmetry are present in the spacer region between rpS11 and its 5' upstream gene rpL36. The deduced amino acid sequence of maize chloroplast S11 shows 69%, 66%, 62%, 57%, 48% and 45% sequence identity to the corresponding sequences of tobacco, spinach, pea, liverwort, Escherichia coli and Bacillus subtilis, respectively, and 41% sequence identity to three eukaryotic cytoplasmic ribosomal proteins, S14 of Chinese hamster and of human and rp59 of yeast. Maize chloroplast r-protein S11 is larger than the other published S11s of plants and bacteria, due to the apparent tandem introduction of a short sequence stretch of internal homology.

Nucleotide sequence and linkage map position of the genes for ribosomal proteins L14 and S8 in the maize chloroplast genome.

The nucleotide sequence of a 1287-base-pair segment of the maize (Zea mays) chloroplast DNA, encoding chloroplast ribosomal proteins L14, S8 and the C-terminal part of L16, has been determined using the dideoxy-chain-termination method. These data from a monocot plant are compared to the corresponding data from a dicot and a lower plant and from two bacteria. The deduced amino acid sequence of maize chloroplast L14 shows 80%, 81%, 51% and 52% and that of S8 shows 75%, 58%, 39% and 38% sequence identity, respectively, to the corresponding sequences of Nicotiana tabacum, Marchantia polymorpha, Bacillus stearothermophilus and Escherichia coli. The starting map coordinates of rpL14 and rpS8 in the physical map of the maize chloroplast DNA [Larrinua, I. M., Muskavitch, K. M. T., Gubbins, E. J. and Bogorad, L. (1983) Plant Mol. Biol. 2, 129-140] are 31.330 and 31.841. The gene order is rpL16-spacer-rpL14-spacer-rpS8. Shine-Dalgarno sequences (GGA and AGGAGG) and computer-derived stem-loop structures of dyad symmetry are present in the spacers and the 3' downstream region of rpS8, respectively, but a chloroplast promoter-like sequence could not be detected suggesting that the latter might be located further upstream in this ribosomal protein gene cluster in maize chloroplast DNA.

Nucleotide sequence and linkage map position of the secX gene in maize chloroplast and evidence that it encodes a protein belonging to the 50S ribosomal subunit.

The nucleotide sequence of the segment of maize chloroplast DNA lying between the map coordinate positions 32.59 and 32.98 Kb and containing the secX gene has been determined. The derived amino acid sequence of maize chloroplast secX is 95%, 87% and 62% identical to the corresponding derived amino acid sequences from two plant chloroplasts and Escherichia coli, respectively. It is also 70% identical to the experimentally determined amino acid sequence of a protein isolated from Bacillus stearothermophilus ribosomes. Separation of the 50S ribosomal subunit proteins of E. coli by reversed phase HPLC gave a peak which contained pure secX protein, as determined by N-terminal amino acid sequencing. Spinach chloroplast 50S subunit proteins separated by HPLC also gave a peak corresponding to pure secX protein. From these results we conclude that the secX gene in E. coli and in plant chloroplasts encodes a small (37-38 amino acid residues) ribosomal protein belonging to the 50S subunit. The same conclusion has been reached recently by A. Wada with respect to E. coli secX. In agreement with Wada, we name the secX protein L36. Its chloroplast gene is designated rpL36.