SecA and the integral membrane proteins SecYEG control almost all protein secretion across the bacterial membrane. A functional copy of SecA is essential for the survival of E. coli. Understanding the structure/function of SecA mutants can provide insight into the function of WT-SecA. Y134S-SecA is a crucial mutant because it can secrete preproteins with a modified signalling peptide more than WT-SecA. Understanding how this mutant affects SecA stability would begin the process of characterizing differences between WT and Y134S-SecA, and contribute to general knowledge of bacterial protein secretion. The objective of this project is to examine differences in structure and stability between WT and Y134S-SecA. The WT-secA- and Y134S-secA- gene was expressed in BL21 E. coli. The resulting protein was purified via Immobilized-Metal Affinity Chromatography, concentrated with a desalting column, and analyzed via tryptophan fluorescence (thermal unfolding from 310-400 nm) at temperatures ranging from 20-60 degrees Celsius. WT and Y134S-SecA had distinct temperatures at which they converted from a folded to fully unfolded state. The mutation of tyrosine to serine at position 134 (WT to Y134S-SecA) resulted in a shift in the unfolding threshold of 2.6 degrees Celsius, indicating that tyrosine residues (amino acid 134 in WT-SecA) play a significant role in SecA stability. Human homologs of the SecA complex (Sec61α) can be compared against SecA to characterize human protein secretion. The position of amino acid 134 between domains of SecA involved in ATP hydrolysis suggests a possible link between protein stability and cell metabolism that can be explored in future research.

Unravelling the structure of SecA: Analysis of WT- vs. Y134S-SecA

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.