Functional studies of Plasmodium falciparum putative SURF1 in Saccharomyces cerevisiae

The mitochondrial electron transport chain (mtETC) of Plasmodium falciparum is an important drug target. Identification and functional validation of putative mitochondrial proteins of the mtETC is critical for drug development. Many of the regulatory subunits and assembly factors of cytochrome c oxidase readily identifiable in humans and yeast are missing in P. falciparum. Here, we describe our efforts to identify and validate the function of putative Pfsurf1, a key assembly factor of complex IV of the mtETC.

Multiple sequence alignment of SURF 1/Shy 1 was carried out in Clustal X 2.1. Phylogenetic tree was constructed using "Draw tree" option in Clustal X, and was analyzed using interactive Tree of Life software. To identify the conserved sequences, domain search was done using Jalview version 2.8.2 (BLOSUM 62 scoring). The haploid Saccharomyces cerevisiae strain (BY4741) containing the null allele shy1 (Orf: YGR112w) (shy1::Kan) was complemented with putative Pfsurf1 to study its ability to rescue the growth defect.

Similarity searches of PfSURF1-like protein in the Pfam shows statistically significant E = 4.7e-10 match to SURF1 family. Sequence alignment of PfSURF1 with other SURF1-like proteins reveals the conservation of transmembrane domains, α-helices and β-pleated sheets. Phylogenetic analysis clusters putative PfSURF1 with apicomplexan SURF1-like proteins. Yeast complementation studies show that Pfsurf1 can partially rescue the yeast shy1 mutant, YGR112w.

Bioinformatics and complementation studies in yeast show that P. falciparum's SURF1 is the functional ortholog of human SURF1 and yeast Shy1.