期刊
BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS
卷 1777, 期 11, 页码 1463-1470出版社
ELSEVIER
DOI: 10.1016/j.bbabio.2008.08.009
关键词
Major light-harvesting a/b complex of; photosystem II; Spectroscopy; Mutagenesis; Low pH
资金
- Marie Curie [MCRTN-CF-2003-505069]
- Hungarian Fund for Basic Research [OTKA K63252]
- Deutsche Forschungsgemeinschaft
- National Natural Science Foundation of China [30470149]
- Knowledge Innovation Program of the Chinese Academy of Sciences [KSCX2-YW-R-137]
- EMBO Shortterm Fellowships [ASTF 190-04]
The major chlorophyll (Chl) a/b complexes of photosystem II (LHCIIb), in addition to their primary light-harvesting function, play key roles in the organization of the granal ultrastructure of the thylakoid membranes and in various regulatory processes. These functions depend on the structural stability and flexibility of the complexes. The lumenal side of LHCIIb is exposed to broadly variable pH environments, due to the build-up and decay of the pH gradient during photosynthesis. Therefore, the negatively charged amino acids in the lumenal loop might be of paramount importance for adjusting the structure and functions of LHCIIb. In order to clarify the structural roles of these residues, we investigated the pigment stoichiometries, absorption, linear and circular dichroism spectra of the reconstituted LHCIIb complexes, in which the negatively charged amino acids in the lumenal loop were exchanged to neutral ones (E94G, E107V and DIM). The mutations influenced the pigment binding and the molecular architecture of the complexes. Exchanging E94 to G destabilized the 3(10) helix in the lumenal loop structure and led to an acquired pH sensitivity of the LHCIIb structure. We conclude that these amino acids are important not only for pigment binding in the complexes, but also in stabilizing the conformation of LHCIIb at different pHs. (C) 2008 Elsevier B.V. All rights reserved.
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