Axial ligation and stoichiometry of heme centers in adrenal cytochrome b561.

Axial ligation and stoichiometry of heme centers in adrenal cytochrome b561. Research Abstract Details 

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Axial ligation and stoichiometry of heme centers in adrenal cytochrome b561. Abstract Text:

Yury Kamensky,Wen Liu,Ah-Lim Tsai,Richard J Kulmacz,Graham Palmer,

Cytochrome (cyt) b561 transports electrons across the membrane of chromaffin granules (CG) present in the adrenal medulla, supporting the biosynthesis of norepinephrine in the CG matrix. We have conducted a detailed characterization of cyt b561 using electron paramagnetic resonance (EPR) and optical spectroscopy on the wild-type and mutant forms of the cytochrome expressed in insect cells. The gz = 3.7 (low-potential heme) and gz = 3.1 (high-potential heme) signals were found to represent the only two authentic hemes of cyt b561; models that propose smaller or greater amounts of heme can be ruled out. We identified the axial ligands to hemes in cyt b561 by mutating four conserved histidines (His54 and His122 at the matrix-side heme center and His88 and His161 at the cytoplasmic-side heme center), thus confirming earlier structural models. Single mutations of any of these histidines produced a constellation of spectroscopic changes that involve not one but both heme centers. We hypothesize that the two hemes and their axial ligands in cyt b561 are integral parts of a structural unit that we term the "kernel". Histidine to glutamine substitutions in the cytoplasmic-side heme center but not in the matrix-side heme center led to the retention of a small fraction of the low-potential heme with gz = 3.7. We provisionally assign the low-potential heme to the matrix side of the membrane; this arrangement suggests that the membrane potential modulates electron transport across the CG membrane.

Axial ligation and stoichiometry of heme centers in adrenal cytochrome b561. Publishing Authors By Initials

Y Kamensky,W Liu,AL Tsai,RJ Kulmacz,G Palmer,

For similar proteins: recombinant proteins research abstracts see: proteins: recombinant proteins research

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Axial ligation and stoichiometry of heme centers in adrenal cytochrome b561. Journal Published:

PUBLICATION TYPE: Research Support, Non-U.S. Gov

Journal: Biochemistry

VOLUME: 46

Page Numbers: 8647-58

Journal Abbreviation: Biochemistry

ISSN: 0006-2960

DAY: 30

MONTH: 06

YEAR: 2007

Axial ligation and stoichiometry of heme centers in adrenal cytochrome b561. Information

Number of References:

LANGUAGE: eng

NlmUniqueID: 370623

Axial ligation and stoichiometry of heme centers in adrenal cytochrome b561. Keywords Mesh Terms:

KEYWORDS: Recombinant Proteins

MESH TERMS: metabolism

Chemical & Substance for Abstract: Axial ligation and stoichiometry of heme centers in adrenal cytochrome b561. Information

Substance Name: Histidine

Registry Number: 71-00-1

Grant and Affiliation Information for Axial ligation and stoichiometry of heme centers in adrenal cytochrome b561.

AFFILIATION: Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77251, USA. yuryk@bioc.rice.edu

Country: United States

AGENCY: United States NIGMS

GRANT: GM44911

ACRONYM: GM

MEDLINETA: Biochemistry

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