Molecular basis of adaptation of seminal proteins of humans and other primates

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Note: This Project Summary is repeated from the parent grant, but with bold highlighting to indicate the portion of the research the undergraduate student, Thomas Washington, will be working on under the proposed Supplement to Promote Diversity in Health-related Research. Project Summary The >20,000 protein-coding genes in our body have been shaped by the combined forces of mutation, natural selection, genetic drift, and migration. An essential way to understand the effects of these forces, especially the consequences of individual amino acid-changing mutations on protein function, is to compare our genes and proteins to those of our closest relatives. In doing so, the mode of selection (positive selection, negative selection, or relaxation of constraint) can also be inferred. Over the last decade, over a dozen high-quality primate genome sequences have been published, allowing for detailed investigation of the forces of evolution acting on the human genome and the genomes of other hominids, using complex models based on the principles of population genetics and molecular evolution. In the proposed research, we will go beyond computational predictions of selection by performing quantitative functional assays using recombinant proteins and synthetic peptides to measure differences in catalytic efficiency and substrate specificity of high-abundant extracellular proteins found in human semen. Such proteins have often been predicted computationally to be the targets of positive selection, purifying selection, and pseudogenization among the hominid primates (humans and the great apes). The experimental design will include testing the function of recombinant proteins from humans, chimpanzees, gorillas, and macaques. Furthermore, we will create the proteins corresponding to the last common ancestors of humans and chimpanzees; of humans, chimpanzees, and gorillas; and of macaques and the hominids, using ancestral sequence reconstruction. For each of these species, we will measure the phosphatase and peptidase activity of the prostatic acid phosphatase ACPP, the protease activity of the prostate expressed KLK3, and the transglutaminase activity of prostatic TGM4. Furthermore, the efficiency and specificity each of these enzymes will be tested using their natural substrates, the seminal vesicle expressed SEMG1 and SEMG2, to understand their coevolution. In addition to examining differences among species in enzyme activity, we will test the hypothesis that species differ in the ability of small peptides derived from ACPP, SEMG1, and SEMG2 to form amyloid fibrils and enhance HIV infection. Finally, we will use bioinformatics approaches to identify primate genes whose evolution may have been driven by either sexual selection or resistance to sexually transmitted viruses. This research will improve undergraduate education at Duquesne University by exposing students to meritorious research while significantly enhancing the research environment of the PI’s laboratory, department, and university.