Purification and Characterization OF HtrA Protein from Lactobacillus acidophilus

Abstract

HtrA is a heat shock-induced serine protease. Homologues of HtrA have been described in a wide range of bacteria and eukaryotes. Its role is to degrade misfolded proteins in the periplasm. As a preliminary step is the understanding of the function of the HtrA protein. Misfolding or unfolding of polypeptides can occur as a consequence of environmental stress and spontaneous mutation. HtrA surface protease in gram-positive bacteria is involved in the processing and maturation of extracellular proteins and degradation of abnormal or misfolded proteins. Inactivation of htrA has been shown to affect the tolerance to thermal and environmental stress and to reduce virulence.The abundance of general chaperones and proteases suggests that cells distinguish between proteins that can be refolded and “hopeless” cases fated to enter the proteolytic pathway. The heat shock protein (HtrA) act as both molecular chaperone and proteolytic activities. The chaperone function dominates at low temperatures, and the proteolytic activity at elevated temperatures. The protease and chaperone activities of HtrA eliminate or refold damaged and unfolded proteins in the bacterial periplasm that are generated upon stress conditions. Function is to protect cells from the deleterious effects of various stress conditions. At temperatures below 28 °C the proteolytic activity of HtrA regarded as negligible and it was believed that the protein mainly plays the role of a chaperone. Substrate recognition probably involves the recently described PDZ domains in the C-terminal half of HtrA. Cells precisely monitor the concentration and functionality of each protein for optimal performance. Protein quality control involves molecular chaperones, folding catalysts, and proteases that are often heat shock proteins. One quality control factor is HtrA, class of oligomeric serine proteases. The defining feature of the HtrA family is the combination of a catalytic domain with at least one C-terminal PDZ domain.