Analysis of Leigh Syndrome Mutations in the Yeast SURF1 Homolog Reveals a New Member of the Cytochrome Oxidase Assembly Factor Family

Authors

Megan Bestwick, University of Utah Health Sciences Center
Mi-Young Jeong, University of Utah Health Sciences Center
Oleh Khalimonchuk, University of Nebraska-LincolnFollow
Hyung Kim, University of Utah Health Sciences Center
Dennis R. Winge, University of Utah Health Sciences Center

Document Type

Article

Date of this Version

2010

Citation

MOLECULAR AND CELLULAR BIOLOGY, Sept. 2010, p. 4480–4491 Vol. 30, No. 18

Comments

Copyright © 2010, American Society for Microbiology. All Rights Reserved.

Abstract

Three missense SURF1 mutations identified in patients with Leigh syndrome (LS) were evaluated in the yeast homolog Shy1 protein. Introduction of two of the Leigh mutations, F²⁴⁹T and Y³⁴⁴D, in Shy1 failed to significantly attenuate the function of Shy1 in cytochrome c oxidase (CcO) biogenesis as seen with the human mutations. In contrast, a G¹³⁷E substitution in Shy1 results in a nonfunctional protein conferring a CcO deficiency. The G¹³⁷E Shy1 mutant phenocopied shy1 Δ cells in impaired Cox1 hemylation and low mitochondrial copper. A genetic screen for allele-specific suppressors of the G137E Shy1 mutant revealed Coa2, Cox10, and a novel factor designated Coa4. Coa2 and Cox10 are previously characterized CcO assembly factors. Coa4 is a twin CX₉C motif mitochondrial protein localized in the intermembrane space and associated with the inner membrane. Cells lacking Coa4 are depressed in CcO activity but show no impairment in Cox1 maturation or formation of the Shy1-stabilized Cox1 assembly intermediate. To glean insights into the functional role of Coa4 in CcO biogenesis, an unbiased suppressor screen of coa4 Δ cells was conducted. Respiratory function of coa4 Δ cells was restored by the overexpression of CYC1 encoding cytochrome c. Cyc1 is known to be important at an ill-defined step in the assembly and/or stability of CcO. This new link to Coa4 may begin to further elucidate the role of Cyc1 in CcO biogenesis.