Structure-Function, Stability, and Chemical Modification of the Cyanobacterial Cytochrome b6f Complex from Nostoc sp. PCC 7120.

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TitleStructure-Function, Stability, and Chemical Modification of the Cyanobacterial Cytochrome b6f Complex from Nostoc sp. PCC 7120.
Publication TypeJournal Article
Year of Publication2009
AuthorsBaniulis, D, Yamashita, E, Whitelegge, JP, Zatsman, AI, Hendrich, MP, S Hasan, S, Ryan, CM, Cramer, WA
JournalJ Biol Chem
Volume284
Issue15
Pagination9861-9
Date Published2009 Apr 10
ISSN0021-9258
KeywordsAmino Acids, Centrifugation, Density Gradient, Crystallography, X-Ray, Cyanobacteria, Cytochrome b6f Complex, Electron Spin Resonance Spectroscopy, Electrons, Heme, Models, Molecular, Nostoc, Plastocyanin, Plastoquinone, Protein Multimerization, Protein Structure, Tertiary, Structure-Activity Relationship
Abstract

The crystal structure of the cyanobacterial cytochrome b(6)f complex has previously been solved to 3.0-A resolution using the thermophilic Mastigocladus laminosus whose genome has not been sequenced. Several unicellular cyanobacteria, whose genomes have been sequenced and are tractable for mutagenesis, do not yield b(6)f complex in an intact dimeric state with significant electron transport activity. The genome of Nostoc sp. PCC 7120 has been sequenced and is closer phylogenetically to M. laminosus than are unicellular cyanobacteria. The amino acid sequences of the large core subunits and four small peripheral subunits of Nostoc are 88 and 80% identical to those in the M. laminosus b(6)f complex. Purified b(6)f complex from Nostoc has a stable dimeric structure, eight subunits with masses similar to those of M. laminosus, and comparable electron transport activity. The crystal structure of the native b(6)f complex, determined to a resolution of 3.0A (PDB id: 2ZT9), is almost identical to that of M. laminosus. Two unique aspects of the Nostoc complex are: (i) a dominant conformation of heme b(p) that is rotated 180 degrees about the alpha- and gamma-meso carbon axis relative to the orientation in the M. laminosus complex and (ii) acetylation of the Rieske iron-sulfur protein (PetC) at the N terminus, a post-translational modification unprecedented in cyanobacterial membrane and electron transport proteins, and in polypeptides of cytochrome bc complexes from any source. The high spin electronic character of the unique heme c(n) is similar to that previously found in the b(6)f complex from other sources.

DOI10.1074/jbc.M809196200
Alternate JournalJ. Biol. Chem.
PubMed ID19189962
PubMed Central IDPMC2665108
Grant ListGM-077387 / GM / NIGMS NIH HHS / United States
GM-38323 / GM / NIGMS NIH HHS / United States
R21RR021913-01A2 / RR / NCRR NIH HHS / United States