title: Factors defining the functional oligomeric state of Escherichia coli DegP protease.
abstract: Escherichia coli DegP protein is a periplasmic protein that functions both as a protease and as a chaperone. In the absence of substrate, DegP oligomerizes as a hexameric cage but in its presence DegP reorganizes into 12 and 24-mer cages with large chambers that house the substrate for degradation or refolding. Here, we studied the factors that determine the oligomeric state adopted by DegP in the presence of substrate. Using size exclusion chromatography and electron microscopy, we found that the size of the substrate molecule is the main factor conditioning the oligomeric state adopted by the enzyme. Other factors such as temperature, a major regulatory factor of the activity of this enzyme, did not influence the oligomeric state adopted by DegP. In addition, we observed that substrate concentration exerted an effect only when large substrates (full-length proteins) were used. However, small substrate molecules (peptides) always triggered the same oligomeric state regardless of their concentration. These results clarify important aspects of the regulation of the oligomeric state of DegP.
authors.affiliation: Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Jack
authors.initials: J
authors.lastname: Iwanczyk
authors.forename: Vivian
authors.initials: V
authors.lastname: Leong
authors.forename: Joaquin
authors.initials: J
authors.lastname: Ortega
mesh_terms: D000595:Amino Acid Sequence; D002364:Caseins / Q000378:metabolism; D020285:Cryoelectron Microscopy; D004926:Escherichia coli / Q000201:enzymology*; D005374:Filtration; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000648:ultrastructure; D008291:Malate Dehydrogenase / Q000378:metabolism; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D033903:Periplasmic Proteins / Q000737:chemistry* / Q000648:ultrastructure; D020836:Protein Structure, Quaternary; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000648:ultrastructure; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D002364:Caseins; D006360:Heat-Shock Proteins; D010455:Peptides; D033903:Periplasmic Proteins; D008291:Malate Dehydrogenase; C061682:DegP protease; D012697:Serine Endopeptidases