Identification of Serine138 Residue in the 4-residue Segment K135K136I137S138 of LukS-I Component of Staphylococcus intermedius Leukocidin Crucial for the LukS-I-specific Function of Staphylococcal Leukocidin(Biochemistry & Molecular Biology)

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Luk-I produced by Staphylococcus intermedius was found to be a new member of the staphylococcal bi-component pore-forming toxin family, in which staphylococcal leukocidin, Panton-Valentine leukocidin, and γ-hemolysin are included. Luk-I consists of LukS-I and LukF-I. From the deduced amino acid sequence of LukS-I, a 4-residue sequence, K135K136I137S138, at the root of the stem region was found to be identical with that of the phosphorylated segment of a protein phosphorylated by protein kinase A. A mutant of LukS-I (MLSI-SA), in which the Ser138 residue was replaced by an alanine residue, was created, purified, and assayed for its leukocytolytic and poreforming activities with LukF-I. Both LukS-I and MLSI-SA formed a ring-shaped complex with LukF-I on rabbit erythrocytes and human polymorphonuclear leukocytes (HPMNLs) membrane. However, MLSI-SA showed no leukocytolytic activity with LukF-I. LukS-I was phosphorylated by protein kinase A in the presence of [γ-^<32>P] ATP in a cell-free system, but MLSI-SA was not phosphorylated significantly. A potent and selective inhibitor of protein kinase A (N- [2(p-bromocinnamylamino) ethyl]-5-isoquinolinesulfonamide (H-89)) showed 50% inhibition of the Luk-I-induced cell lysis at 0.5 nM. Thus, it is concluded that the phosphorylation of the Ser138 residue in the 4-residue segment K135K136I137S138 of LukS-I is important for the leukocytolysis of HPMNLs.
社団法人日本農芸化学会の論文
2002-02-23