CAREER: Folding and Function of Acidophile Proteins

Purdue University, West Lafayette IN

Investigators

Abstract

Acid tolerance is important for industrially useful bacteria, including some organisms that allow internal pH to drop well below neutrality. The entire proteome of these organisms is designed to function at low pH, by global adaptation of each protein for acidic conditions and/or by the action of putative acid chaperones. The goal of this project is to understand acid stable enzymes in Acetobacter aceti, an economically significant, non-pathogenic Gram-negative bacterium that converts ethanol into vinegar, a strong acetic acid solution that kills other microorganisms. Acetic acid seeps constantly into the cytoplasm of A. aceti, which routinely reaches pH 4. Because they have been adapted to function at low pH, cytoplasmic enzymes from A. aceti are excellent models for investigating acid stability in proteins. Biophysical and enzymological methods are used to understand how these proteins fold and function under harsh conditions. Previous studies of thermophilic enzymes have advanced our fundamental understanding of protein structure and provided useful materials for biotechnology (e.g., PCR). This research follows a similar course with a different extreme environment, acidic pH. Design principles derived from these studies may be used to improve biocatalysts and to understand protein folding. Broader impacts: The educational component of this award involves teaching, training and outreach activities. Bioprocess technology requires suitable biocatalysts, enzymes or microbes able to carry out particular chemical transformations. A new practical laboratory experience will be developed to challenge students to find and characterize new pollutant-degrading reactions in microbial bioremediation consortia. Precollege students and science teachers will participate in the selection and improvement of consortia that degrade non-toxic dyes. Students with a range of backgrounds readily grasp the environmental relevance of using microbiological and chemical analysis methods to discover valuable enzymatic activities.