Mutational Analysis of the QRRQ Motif in the Yeast Hig1 Type 2 Protein Rcf1 Reveals a Regulatory Role for the CytochromecOxidase Complex.
The yeast Rcf1 protein is a member of the conserved family of proteins termed the hypoxia-induced gene (domain) 1 (Hig1 or HIGD1) family. Rcf1 interacts with components of the mitochondrial oxidative phosphorylation system, in particular the cytochromebc1(complex III)-cytochromecoxidase (complex IV) supercomplex (termed III-IV) and the ADP/ATP carrier proteins. Rcf1 plays a role in the assembly and modulation of the activity of complex IV; however, the molecular basis for how Rcf1 influences the activity of complex IV is currently unknown. Hig1 type 2 isoforms, which include the Rcf1 protein, are characterized in part by the presence of a conserved motif, (Q/I)X3(R/H)XRX3Q, termed here the QRRQ motif. We show that mutation of conserved residues within the Rcf1 QRRQ motif alters the interactions between Rcf1 and partner proteins and results in the destabilization of complex IV and alteration of its enzymatic properties. Our findings indicate that Rcf1 does not serve as a stoichiometric component,i.e.as a subunit of complex IV, to support its activity. Rather, we propose that Rcf1 serves to dynamically interact with complex IV during its assembly process and, in doing so, regulates a late maturation step of complex IV. We speculate that the Rcf1/Hig1 proteins play a role in the incorporation and/or remodeling of lipids, in particular cardiolipin, into complex IV and. possibly, other mitochondrial proteins such as ADP/ATP carrier proteins.
From the Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin 53233 and.
Joshua
J
Garlich
Functional Proteomics, SFB 815 Core Unit, Goethe-Universität, 60590 Frankfurt am Main, Germany.
Valentina
V
Strecker
Functional Proteomics, SFB 815 Core Unit, Goethe-Universität, 60590 Frankfurt am Main, Germany.
Ilka
I
Wittig
From the Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin 53233 and rosemary.stuart@marquette.edu.
Rosemary A
RA
Stuart
D020816:Amino Acid Motifs / Q000235:genetics*; D002308:Cardiolipins / Q000378:metabolism; D004252:DNA Mutational Analysis; D014450:Electron Transport Complex III / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D024101:Mitochondrial Proteins / Q000378:metabolism; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
D002308:Cardiolipins; D024101:Mitochondrial Proteins; C573148:Rcf1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D003576:Electron Transport Complex IV; D014450:Electron Transport Complex III
Hig1; Rcf1; bioenergetics; cardiolipin; cytochrome c oxidase (complex IV); mitochondria; yeast