Phylogenetic transfer of organelle genes to the nucleus can lead to new mechanisms of protein integration into membranes

Citation
D. Michl et al., Phylogenetic transfer of organelle genes to the nucleus can lead to new mechanisms of protein integration into membranes, PLANT J, 17(1), 1999, pp. 31-40
Citations number
55
Categorie Soggetti
Plant Sciences","Animal & Plant Sciences
Journal title
PLANT JOURNAL
ISSN journal
09607412 → ACNP
Volume
17
Issue
1
Year of publication
1999
Pages
31 - 40
Database
ISI
SICI code
0960-7412(199901)17:1<31:PTOOGT>2.0.ZU;2-M
Abstract
Subunits CFo-I and CFo-II of ATP synthase in chloroplast thylakoid membrane s are two structurally and functionally closely related proteins of bitopic membrane topology which evolved from a common ancestral gene. In higher pl ants, CFo-I still originates in plastid chromosomes (gene: atpF), while the gene for CFo-II (atpG) was phylogenetically transferred to the nucleus. Th is gene transfer was accompanied by the reorganization of the topogenic sig nals and the mechanism of membrane insertion. CFo-I is capable of integrati ng correctly as the mature protein into the thylakoid membrane, whereas mem brane insertion of CFo-II strictly depends on a hydrophobic targeting signa l in the transit peptide. This requirement is caused by three negatively ch arged residues at the hi-terminus of mature CFo-II which are lacking from C Fo-I and which have apparently been added to the protein only after gene tr ansfer has occurred. Accordingly, the CFo-II transit peptide is structurall y and functionally equivalent to typical bipartite transit peptides, capabl e of also translocating hydrophilic lumenal proteins across the thylakoid m embrane. In this case, transport takes place by the Sec-dependent pathway, despite the fact that membrane integration of CFo-II is a Sec-independent, and presumably spontaneous, process.