Abstract
The chloroplast signal recognition particle (cpSRP) consists of a conserved 54 kDa subunit (cpSRP54) and a unique 43 kDa subunit (cpSRP43) but lacks SRP-RNA, an essential and universally conserved component of cytosolic SRPs. High sequence similarity exists between cpSRP54 and bacterial SRP54 except for a plant-specific C-terminal extension containing the cpSRP43-binding motif. We found that cpSRP54 of higher plants lacks the ability to bind SRP-RNA because of two amino acid substitutions within a region corresponding to the RNA binding domain of cytosolic SRP54, whereas the C-terminal extension does not affect RNA binding. Phylogenetic analysis revealed that these mutations occur in the cpSRP54 homologues of higher plants but not in most algae.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Algal Proteins / genetics
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Algal Proteins / metabolism
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Amino Acid Motifs
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Amino Acid Substitution*
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Arabidopsis Proteins / classification
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Arabidopsis Proteins / genetics
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Arabidopsis Proteins / metabolism*
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Bacterial Proteins / genetics
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Bacterial Proteins / metabolism
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Binding Sites / genetics
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Chloroplast Proteins
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Conserved Sequence
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Evolution, Molecular*
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GTP-Binding Proteins / classification
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GTP-Binding Proteins / genetics
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GTP-Binding Proteins / metabolism*
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Molecular Sequence Data
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Mutation
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RNA, Bacterial / metabolism
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RNA, Chloroplast / metabolism
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Signal Recognition Particle / metabolism*
Substances
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Algal Proteins
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Arabidopsis Proteins
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Bacterial Proteins
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Chloroplast Proteins
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RNA, Bacterial
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RNA, Chloroplast
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SRP54A protein, Arabidopsis
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Signal Recognition Particle
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GTP-Binding Proteins