期刊
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
卷 503, 期 4, 页码 3149-3154出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.bbrc.2018.08.108
关键词
Chloroplasts; Hsp70; Protein import; Stromal processing peptidase; Structure; Transit peptide
资金
- NSF [MCB-0719137]
The stromal processing peptidase (SPP) removes transit peptides as precursor proteins enter the chloroplast and different plastid types. SPP is synthesized as a latent, inactive precursor (preSPP) with an atypically long transit peptide. Determinants in the pea (Pisum sativum) SPP transit peptide that regulate mature SPP activation were investigated. Mutational and chemical analyses with protein modifying agents (NEM and APMA) showed a conserved transit peptide Cys-X-Ser/Thr-Cys motif did not inhibit SPP via a cysteine switch mechanism through His-X-X-Glu-His site interactions, although cysteines in mature SPP contribute to an active conformation. Significantly, a transit peptide deletion of only the N-terminal 28 amino acids activates SPP located downstream. Short deletions within this region suggest removal of the initial Met plays a pivotal, mechanistic role. Other deletions of similar to 30 amino acids along the length of the transit peptide do not individually trigger activity, but larger deletions including Met have an additive effect indicating its removal may be a critical early step during preSPP import. Interestingly, the active preSPP deletion mutants no longer possess predicted Hsp70 binding sites including initial Met, thus Hsp70 interactions may restrict SPP from attaining an active conformation. (C) 2018 Elsevier Inc. All rights reserved.
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