Specialized lytic transglycosylases are muramidases capable of locally degrading the peptidoglycan meshwork of Gram-negative bacteria. Specialized lytic transglycosylase genes are present in clusters encoding diverse macromolecular transport systems. This paper reports the analysis of selected members of the specialized lytic transglycosylase family from type III and type IV secretion systems. These proteins were analysed in vivo by assaying their ability to complement the DNA transfer defect of the conjugative F-like plasmid R1-16 lacking a functional P19 protein, the specialized lytic transglycosylase of this type IV secretion system. Heterologous complementation was accomplished using IpgF from the plasmid-encoded type III secretion system of Shigella sonnei and TrbN from the type IV secretion system of the conjugative plasmid RP4. In contrast, neither VirB1 proteins (Agrobacterium tumefaciens, Brucella suis) nor IagB (Salmonella enterica) could functionally replace P19. In vitro, IpgF, IagB, both VirB1 proteins, HP0523 (Helicobacter pylori) and P19 displayed peptidoglycanase activity in zymogram analyses. Using an established test system and a newly developed assay it was shown that IpgF degraded peptidoglycan in solution. IpgF was active only after removal of the chaperonin GroEL, which co-purified with IpgF and inhibited its enzymic activity. A mutant IpgF protein in which the predicted catalytic amino acid, Glu42, was replaced by Gln, was completely inactive. IpgF-catalysed peptidoglycan degradation was optimal at pH 6 and was inhibited by the lytic transglycosylase inhibitors hexa-N-acetylchitohexaose and bulgecin A.

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The spoIIM locus ofBacilus subtilis is the most recently discovered of six genetic loci in which mutations can prevent the synthesis of a normal asymmetric septum or prevent migration of the septal structure to engulf the forespore compartment of the sporangium. Ultrastructure studies of a spoIIM mutant confirmed a block prior to the completion of engulfment. Introduction of a spoIIM mutation into a panel of strains containing lacZ fusions belonging to different regulatory classes allowed us to determine that the spoIIM gene product is required for the efficient expression of genes transcribed by rG-associated RNA polymerase but is not required for the expression of Mr-controlled genes, including spoIIIG, which encodes crG. The results of complementation studies, gene disruption analysis, and DNA sequencing revealed that the spoIIM locus contains a single sporulation-essential gene encoding a polypeptide with a predicted molecular mass of 24,850 Da. The predicted spolIM gene product is highly hydrophobic and very basic, and it does not exhibit significant homology to sequence files in several major data bases.

The release of B19 DNA-positive blood products with a concentration of less than 105 IU per mL is thought to be safe due to the high level of neutralizing VP2 antibodies and is currently examined in a donor recipient infectivity study. In contrast, blood products with a high B19 DNA concentration (> or =10(5) IU/mL), some of which did not contain neutralizing antibodies, were discarded to protect at risk individuals.