The chloroplast-targeting domain of plastocyanin transit peptide can form a helical structure but does not have a high affinity for lipid bilayers.
Conformational properties and interactions with lipid membranes were studied for the chemically synthesized peptides PC(1-37) and PC(1-43), corresponding to the N-terminal 37 and 43 residues, respectively, of the transit peptide of the precursor to plastocyanin of Silene pratensis. PC(1-43) covers the entire chloroplast targeting domain of the transit peptide. CD spectra of PC(1-37) and PC(1-43) showed that both peptides have little ordered structure in aqueous solutions but form partially helical conformations in the presence of detergent micelles or in methanol. Vesicle disruption and direct-binding experiments revealed, however, that neither PC(1-37) nor PC(1-43) had a high affinity for lipid membranes. Since in the intact plastocyanin transit peptide the chloroplast-targeting domain is followed by a hydrophobic thylakoid-transfer domain, the plastocyanin precursor may well be transported to the chloroplast surface first with the aid of the thylakoid-transfer domain. The chloroplast-targeting domain may then form a helical structure in the lipid environments, and a chloroplast-specific motif displayed on the helical structure may be recognized by a receptor protein located at the chloroplast envelope membranes.
Endo
T
T
Department of Chemistry, Faculty of Science, Nagoya University, Japan.
Kawamura
K
K
Nakai
M
M
D000595:Amino Acid Sequence; D002451:Cell Compartmentation; D002736:Chloroplasts / Q000378:metabolism*; D002942:Circular Dichroism; D007425:Intracellular Membranes / Q000378:metabolism; D008051:Lipid Bilayers; D008969:Molecular Sequence Data; D010970:Plastocyanin / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation
D008051:Lipid Bilayers; D010970:Plastocyanin