Conservation of testis protein structure and function revealed in a swapping experiment of human testis tubulin in the fly D. melanogaster
Drosophilid spermtails are the peacock feathers of the world of sperm by virtue of their incredible length, from 2mm in Drosophila melanogaster to over 5cm in D. bifurca. D. melanogaster use a specialized, testis-specific B2 tubulin isoform to generate the microtubule scaffolding of their spermtail axoneme. Structure/function tests show B2 does not tolerate change, even small alterations in its amino acid sequence render it non-functional. This sensitivity is reflected in its evolutionary stasis, the Drosophilid B2 protein has not evolved at a single amino acid in 60 million years. There are two hypotheses for its stasis, either 1) the DmB2 protein is an ideal configuration that has outcompeted variants over the past 60 million years, or 2) it is the only configuration able to support the Drosophilid sperm by evolving into a corner it cannot evolve out of that is resistant to evolutionary change and templates long axonemes. This is tested by assessing the ability of the Homo sapiens sperm-generating beta tubulin protein HsB3 to replace Drosophila B2 in transgenic Drosophila flies. HsB3 is capable of generating sperm, despite being only 90% identical to Drosophila B2. Conversely, a chimeric B1-B2 tubulin over 97% identical to Drosophila B2 cannot. Comparing the 3D protein structures reveals testis tubulins have conserved protein domains and function, indicating convergence on testis-supporting isoforms across deep evolutionary time.
Course Project 202280 BIO 421 P1
Primary Advisor's Department
Stander Symposium, College of Arts and Sciences
Institutional Learning Goals
Scholarship; Vocation; Diversity
"Conservation of testis protein structure and function revealed in a swapping experiment of human testis tubulin in the fly D. melanogaster" (2023). Stander Symposium Projects. 2996.