Conserved loop residues-Tyr and Asn near the catalytic site of the lysostaphin endopeptidase are essential for staphylolytic activity toward pentaglycine binding and catalysis.

Lysostaphin endopeptidase cleaves pentaglycine cross-bridges found in staphylococcal cell-wall peptidoglycans and proves very effective in combatting methicillin-resistant Staphylococcus aureus. Here, we revealed the functional importance of two loop residues, Tyr in loop 1 and Asn in loop 4, which are highly conserved among the M23 endopeptidase family and are found close to the Zn-coordinating active site. Detailed analyses of the binding groove architecture together with protein-ligand docking showed that these two loop residues potentially interact with the docked ligand-pentaglycine.

Cry4Aa and Cry4Ba Mosquito-Active Toxins Utilize Different Domains in Binding to a Particular ALP Isoform: A Functional Toxin Receptor Implicating Differential Actions on Target Larvae.

The three-domain Cry4Aa toxin produced from subsp. was previously shown to be much more toxic to mosquito larvae than its closely related toxin-Cry4Ba. The interaction of these two individual toxins with target receptors on susceptible larval midgut cells is likely to be the critical determinant in their differential toxicity.

Cry4Ba Insecticidal ToxinExploits Leu in Its C-Terminal Domain to Interact with a Target Receptor- Membrane-Bound Alkaline Phosphatase.

In addition to the receptor-binding domain (DII), the C-terminal domain (DIII) of three-domain Cry insecticidal δ-endotoxins from has been implicated in target insect specificity, yet its precise mechanistic role remains unclear. Here, the 21 kDa high-purity isolated DIII fragment derived from the Cry4Ba mosquito-specific toxin was achieved via optimized preparative FPLC, allowing direct rendering analyses for binding characteristics toward its target receptor- membrane-bound alkaline phosphatase (Aa-mALP). Binding analysis via dotblotting revealed that the Cry4Ba-DIII truncate was capable of specific binding to nitrocellulose-bound Aa-mALP, with a binding signal comparable to its 65 kDa Cry4Ba-R203Q full-length toxin.