Cell Wall Hydrolases

Rubens López; Ernesto García; Pedro García; José Luis García

doi:10.1128/9781555816537.ch6

Chapter 6 : Cell Wall Hydrolases

Authors: Rubens López¹, Ernesto García¹, Pedro García¹, José Luis García¹

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Affiliations: 1: Departamento de Microbiología Molecular, Centro de Investigaciones Biológicas, CSIC, E-28040 Madrid, Spain

Content Type: Monograph

Publication Year: 2004

Category: Bacterial Pathogenesis; Clinical Microbiology

Book DOI: 10.1128/9781555816537

Chapter DOI: 10.1128/9781555816537.ch6

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Abstract:

Many bacterial species possess more than one enzyme that hydrolyzes the same bond, a fact that complicates the determination of their biological role(s). This redundancy also contributes to the common thought of assigning a basic role to lytic enzymes in the biology of bacteria. The activity of some pneumococcal murein hydrolases (MHs) appears to be constrained by the membrane lipoteichoic acid (LTA) at the posttranslational level. Cell wall hydrolases (CWHs) of Streptococcus pneumoniae show both substrate and bond specificities. The lytA gene encodes the major S. pneumoniae autolysin (amidase) and represents the first example of a bacterial autolytic gene that was cloned and expressed. LytB is most probably a glucosaminidase capable of degrading Ch-containing cell walls. All the pneumococcal CWHs described have been shown to possess an absolute requirement for the presence of Ch for activity. The cloning of lytA has facilitated the isolation of the genes encoding the cell wall lytic enzymes from pneumococcal bacteriophages based on sequence homologies. This global analysis led the authors to propose that pneumococcal cell wall lytic enzymes could be the result of the fusion of two independent functional domains. The construction of active chimeric proteins between lysins of phage and bacteria led to new enzymes exhibiting novel properties that were, as expected, a combination of those showed by the parental enzymes.

Citation: López R, García E, García P, García J. 2004. Cell Wall Hydrolases, p 75-88. In Tuomanen E, Mitchell T, Morrison D, Spratt B (ed), The Pneumococcus. ASM Press, Washington, DC. doi: 10.1128/9781555816537.ch6

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Cell Wall Hydrolases

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FIGURE 1

Diagrammatic sketch of the cell wall of pneumococci, indicating the chemical bonds cleaved by different CWHs. The peptidoglycan chains and a repeat unit of TA are shown. Abbreviations: G and M, N-acetylglucosamine and N-acetylmuramic acid residues, respectively; Rib, ribitol-5-phosphate; GalNAc, N-acetyl-D-galactosamine; AATGal, 2-acetamido- 4-amino,2,4,6-trideoxy-D-galactose; Glc, Dglucose; ChP, phosphorylcholine.

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FIGURE 1

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FIGURE 2

Schematic representation of the structures of lytA, lytB, lytC, and pce. (A) The genes are labeled as in references 32 and 65 above and below the arrows, respectively. Arrows indicate the direction of transcription of the ORFs. (B) The CWHs are drawn from the NH2 end to the COOH end. Black and dotted bars indicate the parts of the proteins corresponding to the signal peptide and the active center, respectively. Shaded rectangles correspond to the CBRs. aa, amino acids.

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FIGURE 2

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FIGURE 3

Localization of GFP-LytB in the surface of S. pneumoniae. A culture of a lytB mutant of the R6 strain received fusion protein (9.5 μg/ml) and was incubated for 1 min at 37°C. Pictures were taken with a Nikon Eclipse inverted microscope in phase-contrast (a) and using fluorescence (b). Bars, 4 μm. (Reprinted from the Journal of Bacteriology [8] with permission of the publisher.)

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FIGURE 3

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