Functional Analysis of Thiol-Disulfide Oxidoreductases in Streptococcus gordonii

A disulfide bond is a stable bond formed between two molecules of the amino acid cysteine. The formation of disulfide bonds is critical to the stability of the proteins because they allow the proteins to fold into an active conformation (shape) to carry out proper functions or activities. A disulfide bond is formed through the action of enzymes called thiol-disulfide oxidoreductases. In Gram-negative bacteria, the disulfide formation pathway is well understood. In contrast, very little is known about how disulfide bonds are formed in Gram-positive bacteria. The proposed research is designed to understand how disulfide bonds are formed in Gram-positive bacteria using Streptococcus gordonii as a model bacterium. S. gordonii is a normal bacterium found in the human mouth as part of the dental plaque. Because of the changing environment in the mouth from food consumption, saliva flow, and frequent movement of the mouth, S. gordonii has developed many traits to become a successful organism. These traits include the ability to form thick layer of plaque on teeth and pick up DNA from the environment. Proteins involved in these traits contain disulfide bonds and it is our goals to identify the enzymes responsible for forming disulfide bonds in these proteins. We will use modern molecular and biochemical techniques to dissect the exact mechanisms of how disulfide bonds are formed in S. gordonii. Thus, the research provides understanding to protein folding and function that is fundamental to biological processes in a cell.