Lhca5 interaction with plant photosystem I

In the outer antenna (LHCI) of higher plant photosystem I (PSI) four abundantly expressed light-harvesting protein of photosystem I (Lhca)-type proteins are organized in two heterodimeric domains (Lhca1/Lhca4 and Lhca2/Lhca3). Our cross-linking studies on PSI-LHCI preparations from wildtype Arabidopsis and pea plants indicate an exclusive interaction of the rarely expressed Lhca5 light-harvesting protein with LHCI in the Lhca2/Lhca3-site. In PSI particles with an altered LHCI composition Lhca5 assembles in the Lhea1/Lhca4 site, partly as a homodimer. This flexibility indicates a binding-competitive model for the LHCI assembly in plants regulated by molecular interactions of the Lhca proteins with the PSI core. (c) 2006 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.