Pigment complexes of light-harvesting chlorophyll a/b binding protein are stabilized by a segment in the carboxyterminal hydrophilic domain of the protein.
In order to identify segments of light-harvesting chlorophyll a/b-binding protein (LHCP) that are important for pigment binding, we have tested various LHCP mutants regarding their ability to form stable pigment-protein complexes in an in vitro reconstitution assay. Deletion of 10 C-terminal amino acids in the LHCP precursor, pLHCP, did not significantly affect pigment binding, whereas deletion of one additional amino acid, a tryptophan, completely abolished the formation of stable pigment-protein complexes. This tryptophan, however, can be exchanged with other amino acids in full-length pLHCP without noticeably altering the stability or spectroscopic properties of pigment complexes made with these mutants. Thus, the tryptophan residue is not likely to be involved in a highly specific interaction stabilizing the complex. A double mutant of LHCP lacking 66 N-terminal and 6 C-terminal amino acids still forms pigmented complexes that are virtually identical to those formed with the full-length protein concerning their pigment composition and spectroscopic properties. We conclude that about 30% of the polypeptide chain in LHCP is not involved in pigment binding.
Botanisches Institut III der Universität, München, Germany.
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Paulsen
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Kuttkat
D000595:Amino Acid Sequence; D001483:Base Sequence; D002734:Chlorophyll / Q000378:metabolism*; D000077194:Chlorophyll A; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009838:Oligodeoxyribonucleotides; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics / Q000378:metabolism*; D010944:Plants / Q000235:genetics / Q000378:metabolism*; D015183:Restriction Mapping
D009838:Oligodeoxyribonucleotides; D045322:Photosynthetic Reaction Center Complex Proteins; D002734:Chlorophyll; C037184:chlorophyll b; D000077194:Chlorophyll A