The Type Ⅵ secretion system(T6SS)is a versatile and widespread export pathway found in many Gram-negative bacteria that delivers effector proteins into target *** of T6SSs are tightly regulated by diverse mechanisms ...
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The Type Ⅵ secretion system(T6SS)is a versatile and widespread export pathway found in many Gram-negative bacteria that delivers effector proteins into target *** of T6SSs are tightly regulated by diverse mechanisms at multiple levels,including the posttranslational levels through threonine phosphorylation by the Ser/Thr protein kinase(STPK)***,the genetic requirements for PpkA catalysed T6SS in Serratia marcescens and the crystal structure of PpkA kinase domain are *** demonstrated that the PpkA is essential for T6SS secretion since deletion of it eliminated the secretion of hemolysin coregulated protein(Hcp).We further determined the first crystal structures of the kinase domain of PpkA(PpkA-294)in *** structure of PpkA-294 was determined in its apo form to 1.6 ? resolution;in complex with ATP at 1.41 ? and with an ATP analog AMP-PCP to 1.45 ? *** in the activation loop of PpkA-294 were fully determined,and the N-terminal of the loop was folded into an unprecedented inhibitory helix that reveals PpkA kinase domain is in an autoinhibitory *** ternary MgATP-PpkA-294 complexes with novel and invalid conformation of the nucleotide ribose and phosphates are also *** αC-helix in the inactive PpkA-294 adopted a conformation toward the active site,but with the conserved glutamate in the helix rotated away,suggesting a general inactive conformation for inactive STPK *** comparison of PpkA with its eukaryotic homologs reinforces the universal regulation mechanism of protein kinases in eukaryotes and prokaryotes.
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