An investigation of intrinsically disordered proteins in Gram-negative bacteria

Abstract

Sporulation in Gram-positive bacteria results in the production of small acid-soluble proteins (SASPs) to coat the spore DNA and shield it from UV radiation. While orthologs of these SASPs exist in many sporulating and non-sporulating bacteria, they are noticeably absent from the Gram-negative spore-forming Myxococcus xanthus. This is despite the fact that M. xanthus forms spores with enhanced UV resistance compared to their vegetative counterparts. In part I of this thesis, evidence is presented that M. xanthus possesses its own unique set of SASPs that confer UV resistance. Molecular predictions indicate that these SASPs may be membrane associated, which suggests a completely different mechanism than DNA-binding SASPs in Gram-positive species. In part II of this thesis, evidence is shown that non-M. xanthus myxobacteria also possess acid-soluble proteins, and implications are explored. Work using E. coli as a prey source for M. xanthus led to the unexpected discovery that Escherichia coli has its own set of acid-soluble proteins that are primarily associated with the periplasmic region. In Part III of this thesis, the acid-soluble proteins found in E. coli were identified and a survey of Gram-negative species revealed that acid-soluble proteins exist in a wide range of species. The broad implications of these discoveries in the study of proteins with intrinsic disorder are explored, directions for future studies are discussed, and remaining questions are identified.