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Role of the N‐terminal Region in the Function of the Photosynthetic Bacterium Transcription Regulator PpsR †
Author(s) -
Yamazaki Yoichi,
Fukusumi Hayato,
Kamikubo Hironari,
Kataoka Mikio
Publication year - 2008
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.2008.00306.x
Subject(s) - repressor , mutant , psychological repression , dimer , dna , biology , rhodobacter sphaeroides , binding site , dna binding domain , transcription (linguistics) , gene , transcription factor , biochemistry , chemistry , gene expression , photosynthesis , linguistics , philosophy , organic chemistry
PpsR is a transcription repressor for the gene cluster encoding photosystem genes in Rhodobacter sphaeroides. Repression activity is accomplished by DNA binding on the promoter regions of the photosystem gene clusters, and depends on both the redox potential and the presence of antirepressor protein AppA. To understand DNA repression regulation by PpsR, we investigated the function of PpsR domains in self‐association for DNA binding. We constructed domain‐deletion mutants and verified DNA‐binding activity and dimer formation. Gel shift assay for measuring the DNA‐binding activity of three sequential N‐terminal deletion mutants revealed that N‐terminal deletions (of minimum 121 residues) caused loss of binding activity. Size‐exclusion gel chromatography revealed that deletion mutant which lacks the N‐terminal 121‐amino acid deletion mutant to exist as a dimer, although it was less stable than the intact PpsR. The mutants lacking the adjacent regions, Q‐linker region and the first Per‐Ant‐Sim domain, did not form dimers, suggesting the involvement of the N‐terminal region in dimer formation. This region is thus considered to be a functional domain in self‐association, although not yet identified as a structural domain. Circular dichroism spectrum of the N‐terminal region fragment exhibited a α/β structure. We conclude that this region is a structural and functional domain, contributing to PpsR repression through dimer stabilization.