University of Pittsburgh Department of Biological Sciences Presents:
Friday Noon Seminar Series 2017-2018
"Exploiting the business end of MAF1: An interspecific investigation of mitochondrial association factor 1 residues key for function in Toxoplasma gondii"
Friday, October 27, 2017
A219B Langley Hall
12:00 PM Seminar
The functional role of individual protein paralogs expressed from duplicated loci in pathogen virulence and host manipulation is poorly understood. Recent genomic comparisons identified multiple expanded loci in Toxoplasma gondii that are unique compared to close Apicomplexan relatives. One of these loci, mitochondrial association factor 1 (MAF1), encodes distinct paralogs of secreted dense granule effector proteins, some of which mediate the host mitochondrial association (HMA) phenotype (e.g. MAF1b drives HMA, MAF1a does not). Through sequence and functional analysis of all MAF1 paralogs, we have identified regions of the protein that have undergone paralog-specific selection-driven diversification. Using site-directed mutagenesis, we mutated key outward-facing amino acids, proline-rich stretches, and putative phosphorylation sites on MAF1b in an effort to disrupt its ability to mediate HMA. Surprisingly, we found that replacing the 16 C-terminal residues of MAF1b with those of MAF1a completely abrogated MAF1b-mediated HMA. Using recently solved structures of MAF1b and MAF1a, we further identified two critical residues in the C-terminal helix that are required for HMA. Additionally, parasites expressing a functional MAF1b paralog have a significant in vivo competitive advantage in comparison to MAF1b mutants in mice. Taken together, the significance of the MAF1b C-terminus in HMA and its in vivo advantage provide the tools necessary to probe the function of MAF1b and significance of HMA in T. gondii interactions with its host.