title: Structural and EPR characterization of the soluble form of cytochrome c-550 and of the psbV2 gene product from the cyanobacterium Thermosynechococcus elongatus.
abstract: First, the crystal structure of cytochrome c-550 (the psbV1 gene product) from the thermophilic cyanobacterium Thermosynechococcus elongatus has been determined to a resolution of 1.8 A. A comparison of the T. elongatus cytochrome c-550 structure to its counterparts from mesophilic organisms, Synechocystis 6803 and Arthrospira maxima, suggests that increased numbers of hydrogen bonds may play a role in the structural basis of thermostability. The cytochrome c-550 in T. elongatus also differs from that in Synechocystis 6803 and Arthrospira maxima in its lack of dimerization and the presence of a trigonal planar molecule, possibly bicarbonate, tightly bound to the heme propionate oxygen atoms. Cytochromes c-550 from T. elongatus, Synechocystis 6803 and Arthrospira maxima exhibit different EPR spectra. A correlation has been done between the heme-axial ligands geometries and the rhombicity calculated from the EPR spectra. This correlation indicates that binding of cytochrome c-550 to Photosystem II is accompanied by structural changes in the heme vicinity. Second, the psbV2 gene product has been found and purified. The UV-visible, EPR and Raman spectra are reported. From the spectroscopic data and from a theoretical structural model based on the cytochrome c-550 structure it is proposed that the 6th ligand of the heme-iron is the Tyr86.
authors.affiliation: Molecular Biology Institute, UCLA, Box 951570, Los Angeles, CA 90095-1570, USA. kerfeld@mbi.ucla.edu
authors.forename: Cheryl A
authors.initials: CA
authors.lastname: Kerfeld
authors.forename: Michael R
authors.initials: MR
authors.lastname: Sawaya
authors.forename: Hervé
authors.initials: H
authors.lastname: Bottin
authors.forename: Kimberlee T
authors.initials: KT
authors.lastname: Tran
authors.forename: Miwa
authors.initials: M
authors.lastname: Sugiura
authors.forename: Duilio
authors.initials: D
authors.lastname: Cascio
authors.forename: Alain
authors.initials: A
authors.lastname: Desbois
authors.forename: Todd O
authors.initials: TO
authors.lastname: Yeates
authors.forename: Diana
authors.initials: D
authors.lastname: Kirilovsky
authors.forename: Alain
authors.initials: A
authors.lastname: Boussac
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D003460:Crystallization; D000458:Cyanobacteria / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D003574:Cytochrome c Group / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D006420:Hemeproteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D015394:Molecular Structure; D021281:Quantitative Structure-Activity Relationship; D017386:Sequence Homology, Amino Acid; D012995:Solubility; D013059:Spectrum Analysis, Raman; D014466:Ultraviolet Rays
chemical_list: D001426:Bacterial Proteins; D003574:Cytochrome c Group; D006420:Hemeproteins; C031732:cytochrome C-550