In green: Asp136 – phosphorylation site and Lys42 – ATP binding site. The amino acid substitutions, relative to the R6 sequence, are in red: Arg45Lys, Ala113Val, Asn227Lys and Ser237Pro. (B) Image of computed molecular

surface of StkP kinase domain (4–274). The colours are otherwise as in Fig. 2A. To evaluate the consequences of mutations Wee1 inhibitor in the PASTA domains on the penicillin susceptibility of clinical isolates we analysed the genetic polymorphism of PBP2B, PBP2X and PBP1A, in relation the PASTA alleles in the different isolates (Additional file 1: Table ST1). RFLP patterns 4, 5, 7, 9, 18 of PBP2B, patterns 5 to 9 of PBP2X and patterns 4 to 10, 13, 16 and 17 of PBP1A (see Additional file 1: Tables ST2, Akt inhibitor ST3 and ST4) are not associated with mutations involved in penicillin resistance, according to previous descriptions [22–30]. Four PASTA alleles (StkP alleles: 3, 7, 10 and 11) were only found in sensitive CP673451 supplier strains (URA3826, URA5133, URA3537, URA3388, URA3444, URA6035, URA4549). These strains showed PBP profiles characteristic of sensitive strains, suggesting that their MICs were

determined by their PBPs rather than mutation in their PASTA sequence. The other PASTA alleles were found in all the three classes of strains (high and intermediate resistance, and susceptibility) suggesting that this allele did not affect the MIC. We checked, for each strain, that the resistance character corresponded to the PBP profile (Additional file 1: Table ST1). Findings for strain URA5132 were, however, more ambiguous: it was susceptible with a MIC of 0.006 μg ml-1 despite carrying the PBP2X mutations Arg384Gly and Gln552Glu related to resistance [22]; it also carries the Val623Ala PASTA allele suggesting that it may have a putative suppressor function leading to the susceptible phenotype. However, we did not test whether the

PASTA Val623Ala allele is directly involved as a suppressor of the PBP mutations, http://www.selleck.co.jp/products/Staurosporine.html partly because mutation Val623Ala is the replacement of one non polar amino acid with another. Note that this mutation was also found in resistant (URA5805 and URA4203) and intermediate (URA4566, URA4731 and URA5779) strains and therefore it is unlikely that it determines the penicillin susceptibility of strain URA5132. Discussion This work presents two different approaches for the evaluation of StkP on penicillin susceptibility. By the Cp1015 model system, we present genetic and physiological evidence of the involvement of the serine threonine kinase StkP in cell wall metabolism upstream from the steps catalysed by penicillin binding proteins PBP2B, 2X and 1A in S. pneumoniae. The second approach allowed us to observe that StkP is genetically conserved among clinical strains, regardless of penicillin susceptibility or site of isolation. Indeed, no change of genetic diversity or any specific amino acid substitution was found to be related to isolates recovered from invasive disease or colonizing strains.