The oligomeric state of the Caldivirga maquilingensis type III sulfide:Quinone Oxidoreductase is required for membrane binding

Publication date: Available online 6 December 2019Source: Biochimica et Biophysica Acta (BBA) - BioenergeticsAuthor(s): Andrea M. Lencina, Robert B. Gennis, Lici A. Schurig-BriccioAbstractSulfide:quinone oxidoreductase (SQR) is a monotopic membrane flavoprotein present in all domains of life, with multiple roles including sulfide detoxification, homeostasis and energy generation by providing electrons to respiratory or photosynthetic electron transport chains. A type III SQR from the hyperthermophilic archeon Caldivirga maquilingensis has been previously characterized, and its C-terminal amphipathic helices were demonstrated to be responsible for membrane binding. Here, the oligomeric state of this protein was experimentally evaluated by size exclusion chromatography, native gels and crosslinking, and found to be a monomer-dimer-trimer equilibrium. Remarkably, mutant and truncated variants unable to bind to the membrane are able to maintain their oligomeric association. Thus, unlike other related monotopic membrane proteins, the region involved in membrane binding does not influence oligomerization. Furthermore, by studying heterodimers between the WT and mutants, it was concluded that membrane binding requires an oligomer with at least two copies of the protein with intact C-terminal amphipathic helices. A structural homology model of the C. maquilingensis SQR was used to define the flavin- and quinone-binding sites. CmGly12, CmGly16, CmAla77 and CmPro44 were determined to b...
Source: Biochimica et Biophysica Acta (BBA) Bioenergetics - Category: Biochemistry Source Type: research