The secondary structure of the ferredoxin transit sequence is modulated by its interaction with negatively charged lipids

Abstract

Import of proteins into chloroplasts depends on an N-terminal transit sequence. Transit sequences contain little primary sequence similarity and therefore recognition of these sequences is thought to involve specific folding. To assess the conformational flexibility of the transit sequence, we studied the transit peptide of preferredoxin (trfd) by circular dichroism. In buffer, trfd is in a random coil conformation. A large increase in ~-helix was induced in the presence of micelles or vesicles formed by anionic lipids. Less pronounced changes in secondary structure were induced by zwitterionic detergents but no changes were observed in the presence of neutral detergents or vesicles composed of phosphatidylcholine.

In Vitro Interaction between a Chloroplast Transit Peptide and Chloroplast Outer Envelope Lipids Is Sequence-specific and Lipid Class-dependent

“…The finding that SS-tp-(41-60) was more disruptive to the OM liposomes than SS-tp- (31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50) suggests that the C-terminal 10 amino acids of the SS-tp are the most "membrane-active" region of the 60 amino acid SS-tp. Therefore, the precursor/ lipid interaction was mediated primarily via the extreme C terminus of SS-tp.…”

Protein Translocation at the Envelope and Thylakoid Membranes of Chloroplasts

“…29). Of particular interest is the observation that the lipid-protein interactions induce regular secondary structure into the normally disordered structure of transit sequences observed in aqueous solutions (30). These observations suggest that an initial, reversible interaction of transit sequences with the lipid component of the bilayer may induce regular structure, thereby facilitating the binding of the transit sequence to receptor components of the import machinery.…”

Transit sequence‐dependent binding of the chloroplast precursor protein ferredoxin to lipid vesicles and its implications for membrane stability

“…NMR experiments with lipid dispersions revealed that precursor protein-lipid interactions result in transit sequence mediated changes in the lipid organization [7]. The lipid-protein interactions are accompanied by the induction of secondary structure in the other wise unstructured transit peptide [8].…”