Substitution of lysine for arginine in the N-terminal 217th amino acid residue of the H gamma II of Staphylococcal gamma-hemolysin lowers the activity of the toxin

Prophage, phiPV83-pro, carrying panton-valentine leukocidin genes, on the Staphylococcus aureus P83 chromosome: comparative analysis of the genome structures of phiPV83-pro, phiPVL, phi11, and other phages

Staphylococcus aureus P83 has Panton-Valentine leukocidin (PVL)-like genes, lukM and lukF-PV. Here, lukM and lukF-PV genes were found on the genome of a prophage, which was designated as phiPV83-pro. The precise genome size was 45,636 bp with att core sequences of 10 base pairs. Sixty-four ORFs were identified on the phiPV83-pro genome, including two extra operons, lukM-lukF-PV and orfs63-64. The lukM-lukF-PV cluster was located 2.1 kb upstream of the attL site. The most striking feature of the phiPV83-pro genome was a constituent of at least 4 regions from phi11, phiPVL, and other phages, i.e., (i) att sites identical with those of phi11, (ii) a cos sequence and the genes encoding packaging and head proteins of phiPVL (occupied half region of phiPV83-pro), and (iii) the other two regions which showed no significant similarity with known phages (occupied about 40% of phiPV83-pro). Furthermore, two insertion sequences, ISSA1 and ISSA2 were integrated into attL site and orf44, respectively. PhiPV83-pro was not induced as phage particles from S. aureus P83 regardless of its treatment with mitomycin C. The insertion of ISSA1 into the attL site was one of the reasons of the failure of the induction of the phage particles by mitomycin C treatment of the strain P83.

Further study on the two pivotal parts of Hlg2 for the full hemolytic activity of staphylococcal gamma-hemolysin

Staphylococcal gamma-hemolysin consists of LukF of 34 kDa and Hlg2 (or H gamma II) of 32 kDa, which cooperatively lyse human and rabbit erythrocytes. Our previous data showed that the 5-residue segment K23R24L25A26I27 of Hlg2 is pivotal for the hemolytic activity [Nariya, H. and Kamio, Y., Biosci. Biotechnol. Biochem., 59, 1603-1604 (1997)]. Here, we identify an additional amino acid residue in Hlg2 necessary for the full gamma-hemolysin activity by measuring the toxin activity of Hlg2 mutants in the presence of LukF. The data obtained showed that Arg217 of Hlg2 is an additional pivotal amino acid residue besides the KRLAI segment for the full Hlg2-specific function in gamma-hemolysin. We also report evidence that the Hlg2 mutants showing a low or null hemolytic activity in the presence of LukF towards human erythrocytes had low or no binding activity to the cells, resulting in failure of formation of the ring-shaped pore-forming complex on the erythrocytes.

Phosphorylation of LukS by protein kinase A is crucial for the LukS-specific function of the staphylococcal leukocidin on human polymorphonuclear leukocytes

Staphylococcal leukocidin (Luk) consists of two protein components, LukF and LukS, which cooperatively lyse human and rabbit polymorphonuclear leukocytes. Here, we demonstrate that the phosphorylation of LukS by protein kinase A is crucial for the LukS-specific leukocytolytic function of Luk on HPMNLs by using N-[2(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide (H-89), which is a potent and selective inhibitor of protein kinase A. At 0.5 microM H-89 completely prevented the Luk-induced cell lysis accompanied by blocking of the incorporation of exogenous 32P-H3PO4 into LukS on HPMNLs. However, with LukS and LukF together, 0.5 microM H-89 did not inhibit the cell swelling which takes place before the cell lysis. HPMNLs also became swollen upon treating with both LukF and LukS mutants which could not be phosphorylated.

Molecular properties and activity of a carboxyl-terminal truncated form of xylanase 3 from Aeromonas caviae W-61

Aeromonas caviae W-61 produces five species of xylanases, xylanases 1, 2, 3, 4, and 5 [Nguyen, V.D. et al., Biosci. Biotechnol. Biochem., 56, 1708-1712 (1993) and Appl. Environ. Microbiol., 57, 445-449 (1991)]. While preserving a purified xylanase 3 preparation from A. caviae in solution at 4 degrees C, the xylanase 3 was found to be proteolyzed to give a truncated form with a smaller molecular mass than that of the intact one. It appears likely that the truncated form of xylanase 3 was produced in this particular purification experiment by the action of a contaminating protease. We isolated the truncated form of xylanase 3 (Xyn3tr), of which the C-terminal 102-residue segment is missing. By the chemical analysis of the N- and C-terminal amino acid residues of Xyn3tr and the DNA sequencing analysis of the xylanase 3 gene (xyn3), the N-terminal 398th proline residue of xylanase 3 was found to be the C-terminus of Xyn3tr. Xyn3tr had the activity to form xylotriose (X3), xylotetraose (X4), xylopentaose (X5), and xylohexaose (X6) as main final products from oat spelt xylan. In contrast, intact xylanase 3 released X6 and higher xylo-oligosaccharides as main products. Xylanase 3 hydrolysed X4 through X6. However, Xyn3tr had no activity towards X4 and X5. The recombinant Xyn3tr and recombinant xylanase 3 (XYN3) were purified homogeneously from the periplasmic space of E. coli harboring the plasmids pXYN3 and pXYN3tr, which include xyn3 and xyn3tr genes, respectively, and their enzymatic activities were measured. The cleavage patterns of oat spelt and xylo-oligosaccharides by XYN3tr were identical with that by intact Xyn3tr. Thus, we conclude that the C-terminal region comprising a 102-residue segment in xylanase 3 is involved in governing the molecular size of xylo-oligosaccharides cleaved from beta-1,4-xylan by the enzyme and in the hydrolytic activity towards X4 and X5.

The genome of Staphylococcus aureus: a review

The genome of Staphylococcus aureus consists of a single circular chromosome (2.7-2.8 mbp) plus an assortment of extrachromosomal accessory genetic elements: conjugative and nonconjugative plasmids, mobile elements (IS, Tn, Hi), prophages and other variable elements. Plasmids (1-60 kbp) are classified into 4 classes and there are 15 known incompatibility groups. Mobile elements of the genome (0.8-18 kbp) appear in the chromosome or in plasmids of classes II and III. Prophages (45-60 kbp) are integrated in the bacterial chromosome, and they are UV- or mitomycin-inducible. Temperate bacteriophages of S. aureus are members of the Siphoviridae and the serological groups A, B and F occur most frequently. In the paper presented, the characteristics of chromosome, plasmids, transposons and other genetic elements of S. aureus genome are given and an alphabetical list of known genes of this species is included.