Conformational dynamics of the essential sensor histidine kinase WalK

Abstract

Two-component systems (TCSs) are key elements in bacterial signal transduction in response to environmental stresses. TCSs generally consist of sensor histidine kinases (SKs) and their cognate response regulators (RRs). Many SKs exhibit autokinase, phosphoryltransferase and phosphatase activities, which regulate RR activity through a phosphorylation and dephosphorylation cycle. However, how SKs perform different enzymatic activities is poorly understood. Here, several crystal structures of the minimal catalytic region of WalK, an essential SK from Lactobacillus plantarum that shares 60% sequence identity with its homologue VicK from Streptococcus mutans, are presented. WalK adopts an asymmetrical closed structure in the presence of ATP or ADP, in which one of the CA domains is positioned close to the DHp domain, thus leading both the -and -phosphates of ATP/ADP to form hydrogen bonds to the "-but not the -nitrogen of the phosphorylatable histidine in the DHp domain. In addition, the DHp domain in the ATP/ADP-bound state has a 25.7 asymmetrical helical bending coordinated with the repositioning of the CA domain; these processes are mutually exclusive and alternate in response to helicity changes that are possibly regulated by upstream signals. In the absence of ATP or ADP, however, WalK adopts a completely symmetric open structure with its DHp domain centred between two outward-reaching CA domains. In summary, these structures of WalK reveal the intrinsic dynamic properties of an SK structure as a molecular basis for multifunctionality.

Revisiting the pH-gated conformational switch on the activities of HisKA-family histidine kinases

“…HK853 structures reported here and the previously deposited in the PDB show that His260 side chain interact with the main chain oxygen of residue at position −4 (A256 in HK853) when adopts the gauche− rotamer. Similar interactions are observed for the phosphorylatable His in the CpxA (PDB 4BIX) 8 , WalK (PDB 5C93) 17 , VicK (PDB 4I5S) 20 , and PhoR (PDB 5UKV) 21 HKs, supporting that this interaction would be stabilizing the rotamer disposition. Close inspection of the His260 in the HK-RR pHs structures showed that this residue was also interacting with a sulfate ion through its side-chain Nε (Fig.…”

“…2). Finally, we looked for the presence of a sulfate ion coordinated to the phosphorylatable His in other structures of HisKA family and we found that WalK (PDB 5C93), which was crystalized in presence of high concentration of sulfate (1.0 M ammonium sulfate) 17 , coordinated a sulfate ion in an equivalent position as HK853. In WalK the phosphorylatable His (His386) presented both trans and gauche− rotamers but the sulfate ion was coordinated to the gauche− rotamer ( Supplementary Fig.…”

Hybrid histidine kinase activation by cyclic di-GMP-mediated domain liberation

“…7c), which would be sterically incompatible with an analogous motion of α1 of the other subunit. This has been discussed and analyzed thoroughly by 15 Bhate and coworkers 6 and corroborated by the recent structure and modelled dynamics of WalK 25 .…”

Hybrid histidine kinase activation by cyclic di-GMP–mediated domain liberation

“…7C), which would be sterically incompatible with an analogous motion of α1 from the other subunit. This has been discussed and analyzed thoroughly by Bhate et al (9) and corroborated by the recent structure and modeled dynamics of WalK (35). The DHp domain of ShkA belongs to the major HisKA pfam family (36) that exhibits a HxxxxP motif (Fig.…”