Three-dimensional structure and molecular mechanism of novel enzymes of spore-forming bacteria

Bacillus and Clostridium species are spore-forming bacilli that cause serious diseases in livestock and in humans. An important pathogen in this group of organisms is Bacillus anthracis is which is the causative agent of anthrax. The biochemical properties, structure, function, and mechanism of catalysis of the novel spore germination protease (GPR) that degrades small, acid soluble proteins (SASP) protecting spore's DNA against damage and a novel, cofactor independent phosphoglycerate mutase (iPGM) are described. A coat created from SASP synthesized during sporulation protects DNA in spores and later in the germination this protective coat is removal by a novel GPR protease. GPR does not resemble in its structure any other known protein and functionally likely belongs to a novel class of proteases utilizing glutamic acid residue in its catalysis in order to degrade SASP. This process provides amino acids necessary for synthesis of other proteins or enzymes necessary in vegetative state. In addition during the spore creation process energy is stored in the form of 3-phosphoglycerate by downregulating a novel, diphosphoglycerate independent iPGM. These depots of energy are utilized later by the germinating spore in addition to the above source of amino acids. The two above enzymes are inherently involved in the processes of sporulation, spore germination and outgrowth. A combination of structural investigations and site-directed mutagenesis studies that were used to characterize the functional properties and the active sites of these novel proteins will be discussed. The understanding of functional properties of these enzymes contributes to a better understanding of spore-forming organisms.