Biological role of the pneumococcal amidase

Abstract

A pneumococcal recombinant plasmid, pRG2, containing the ZytA gene that codes for the pneumococcal N-acetylmuramoyl-~-alanine amidase has been constructed using the pneumococcal plasmid pLSl as a vector. pRG2 was introduced by genetic transformation into a mutant of Streptococcus pneumoniae (M31) that has a complete deletion of the lytA gene. The transformed strain (M51) grew at a normal growth rate as 'diplo' cells and underwent autolysis at the end of the exponential phase of growth, two properties that had been lost in the deleted mutant M31. M51 lysed very rapidly at the end of the exponential phase when the cells were grown in choline-containing medium probably because of the higher level of amidase activity present in this strain as compared to the lysis-prone strain M11. These findings show that the expression of the plasmid-linked gene was placed under the mechanism(s) of control of the cell during the exponential phase. Our results demonstrate that the physiological role of the pneumococcal amidase was to catalyze the separation of the daughter cells at the end of the cell division to produce diplo cells; in addition we have also confirmed the basic role of this autolysin in the bacteriolytic nature of P-lactam antibiotics.

Genome-Based Bioinformatic Selection of ChromosomalBacillus anthracisPutative Vaccine Candidates Coupled with Proteomic Identification of Surface-Associated Antigens

“…There is growing evidence of the contribution of autolysins to microbial virulence (55). For example, LytA amidase from Streptococcus pneumoniae (82), was shown to induce a protective response when inoculated into the lungs of mice (33). The three Streptococcal cell wall hydrolases (LytA, LytB, and LytC), anchored to the membrane via teichoic acid residues, were recently shown to affect colonization in the nasopharynx in S. pneumoniae.…”

Pneumococcal Virulence Factors: Structure and Function

“…The major function of this group of enzymes, cell wall degradation, has significant physiological consequences, such as cell lysis which leads directly to cell death (152,156). An example of one such enzyme is the S. pneumoniae N-acetylmuramoyl-L-alanine amidase, also known as LytA amidase (91,127). It probably is the best characterized autolysin of this group of enzymes, and it has been implicated in the pathogenicity of pneumococci.…”

“…Examples of other pneumococcal CBPs are the major cell wall hydrolase LytA (54) and an adhesin choline binding protein A (CbpA) (129). LytA is an amidase functioning in the separation of daughter cells during cell division (127) and is required for cell lysis (155), whereas CbpA appears to be the first known protein adhesin on the pneumococcal surface (129). The CBR motif has also been found among the surface proteins of other bacteria (164) like Clostridium acetobutylicum, Clostridium difficile, Streptococcus mutans, and Streptococcus downei.…”

Intact Bacteria Inhibit the Induction of Humoral Immune Responses to Bacterial-Derived and Heterologous Soluble T Cell-Dependent Antigens

“…Thus, secreted hydrolases such as hyaluronidases, neuraminidases, and endoglycosidases can mediate bacterial spread and destruction of host tissue through degradation of hyaluronan, mucins, and glycolipids. Additionally, during the stationary growth phase, Pn expresses a major autolysin (LytA amidase) that degrades its own peptidoglycan cell wall, resulting in release of cytoplasmic proteins (3,4). One such protein is pneumolysin, which can induce host cell injury through formation of cell membrane pores (5) and at lower concentrations can stimulate release of proinflammatory mediators (6) and directly accelerate cell death of neutrophils (7), the major phagocytic cell that mediates innate immunity to extracellular bacteria.…”