Light-inducible gene HSP70B encodes a chloroplast-localized heat shock protein in Chlamydomonas reinhardtii.
The nuclear heat shock gene HSP70B of Chlamydomonas reinhardtii is inducible by heat stress and light. Induction by either environmental cue resulted in a transient elevation in HSP70B protein. Here we describe the organization and nucleotide sequence of the HSP70B gene. The deduced protein exhibits a distinctly higher homology to prokaryotic HSP70s than to those of eukaryotes, including the cytosolic HSP70A of Chlamydomonas reinhardtii. The HSP70B protein, as previously demonstrated by in vitro translation, is synthesized with a cleavable presequence. Using an HSP70B-specific antibody, this heat shock protein was localized to the chloroplast by cell fractionation experiments. A stromal location was suggested by the presence of a conserved sequence motif used for cleavage of presequences by a signal peptidase of the stroma. Amino acid alignments of HSP70 proteins from various organisms and different cellular compartments allowed the identification of sequence motifs, which are diagnostic for HSP70s of chloroplasts and cyanobacteria.
Institut für Biologie III, Universität Freiburg, Germany.
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Drzymalla
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Schroda
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Beck
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002451:Cell Compartmentation; D016825:Chlamydomonas reinhardtii / Q000235:genetics* / Q000528:radiation effects; D002736:Chloroplasts / Q000737:chemistry*; D029968:Escherichia coli Proteins; D005786:Gene Expression Regulation; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis / Q000235:genetics*; D018869:Heat-Shock Response; D008027:Light; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D010940:Plant Proteins; D011498:Protein Precursors / Q000235:genetics; D011499:Protein Processing, Post-Translational; D015800:Protozoan Proteins; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000378:metabolism; D013347:Subcellular Fractions / Q000737:chemistry
D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; C102156:HSP70B protein, Chlamydomonas; D008565:Membrane Proteins; D010940:Plant Proteins; D011498:Protein Precursors; D015800:Protozoan Proteins; D012697:Serine Endopeptidases; C026515:type I signal peptidase; C063842:dnaK protein, E coli