1CSW

REPLACEMENTS IN A CONSERVED LEUCINE CLUSTER IN THE HYDROPHOBIC HEME POCKET OF CYTOCHROME C

1CSW の概要

• エントリーDOI: 10.2210/pdb1csw/pdb
• 関連するPDBエントリー: 1ycc
• 分子名称: CYTOCHROME C, SULFATE ION, HEME C, ... (4 entities in total)
• 機能のキーワード: electron transport(heme protein)
• 由来する生物種: Saccharomyces cerevisiae (baker's yeast)
• 細胞内の位置: Mitochondrion intermembrane space: P00044
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 12846.48

構造登録者

Lo, T.P.,Brayer, G.D. (登録日: 1994-10-04, 公開日: 1995-01-26, 最終更新日: 2021-03-10)

主引用文献

Lo, T.P.,Murphy, M.E.,Guillemette, J.G.,Smith, M.,Brayer, G.D.
Replacements in a conserved leucine cluster in the hydrophobic heme pocket of cytochrome c.
Protein Sci., 4:198-208, 1995

PubMed Abstract: A cluster of highly conserved leucine side chains from residues 9, 68, 85, 94, and 98 is located in the hydrophobic heme pocket of cytochrome c. The contributions of two of these, Leu 85 and Leu 94, have been studied using a protein structure-function-mutagenesis approach to probe their roles in the maintenance of overall structural integrity and electron transfer activity. Structural studies of the L85C, L85F, L85M, and L94S mutant proteins show that, in each case, the overall fold of cytochrome c is retained, but that localized conformational shifts are required to accommodate the introduced side chains. In particular, the side chains of Cys 85 and Phe 85 form energetically favorable interactions with Phe 82, whereas Met 85 takes on a more remote conformation to prevent an unfavorable interaction with the phenyl ring of Phe 82. In the case of the L94S mutant protein, the new polar group introduced is found to form hydrogen bonds to nearby carbonyl groups. In all proteins with substitutions at Leu 85, the hydrophobic nature of the heme pocket is preserved and no significant decrease in heme reduction potential is observed. Despite earlier predictions that Leu 85 is an important determinant in cytochrome c electron transfer partner complexation, our studies show this is unlikely to be the case because the considerable surface contour perturbations made by substitutions at this residue do not correspondingly translate into significant changes in electron transfer rates. For the L94S mutant protein, the substitution of a polar hydroxyl group directly into the hydrophobic heme pocket has a larger effect on heme reduction potential, but this is mitigated by two factors. First, the side chain of Ser 94 is rotated away from the heme group and, second, the side chain of Leu 98 shifts into a portion of the new space available, partially shielding the heme group. The Leu 94 Ser substitution does not perturb the highly conserved interface formed by the nearly perpendicular packing of the N- and C-terminal helices of cytochrome c, ruling this out as the cause of this mutant protein becoming thermally labile and having a lower functional activity. Our results show these effects are most likely attributable to disruption of the heme pocket region. Much of the ability of cytochrome c to absorb the introduction of mutations at Leu 85 and Leu 94 appears to be a consequence of the conformational flexibility afforded by the leucine cluster in this region as well as the presence of a nearby internal cavity.(ABSTRACT TRUNCATED AT 400 WORDS)

PubMed: 7757009

実験手法

X-RAY DIFFRACTION (1.9 Å)