Interhelical H-Bonds Modulate the Activity of a Polytopic Transmembrane Kinase.

Juan Cruz Almada,Jean Marie Ruysschaert,Diego De Mendoza,Ana Bortolotti,Larisa Estefanía Cybulski,María Eugenia Inda

doi:10.3390/biom11070938

Abstract

DesK is a Histidine Kinase that allows Bacillus subtilis to maintain lipid homeostasis in response to changes in the environment. It is located in the membrane, and has five transmembrane helices and a cytoplasmic catalytic domain. The transmembrane region triggers the phosphorylation of the catalytic domain as soon as the membrane lipids rigidify. In this research, we study how transmembrane inter-helical interactions contribute to signal transmission; we designed a co-expression system that allows studying in vivo interactions between transmembrane helices. By Alanine-replacements, we identified a group of polar uncharged residues, whose side chains contain hydrogen-bond donors or acceptors, which are required for the interaction with other DesK transmembrane helices; a particular array of H-bond- residues plays a key role in signaling, transmitting information detected at the membrane level into the cell to finally trigger an adaptive response.

Highlights

Histidine kinases (HK) are the sensory proteins of two-component systems
In order to discern whether both catalytic domains fused either to TM1 or TM5 were equivalent in their capacity to process the input signal, we introduced a mutation in the catalytic residue H188.The cytoplasmic domain has two domains: the catalytic and ATPbinding domain (CA) and the Dimerisation and Histidine phosphotransfer domain
Extensive efforts and resources have been destined to study transmembrane kinases; many questions remain about the structural mechanism by which signals pass from the extracellular sensors to the cytoplasmic catalytic domain

Summary

Introduction

Histidine kinases (HK) are the sensory proteins of two-component systems. They perceive and respond to a broad range of stimuli that may imply general stress or specific signals, such as the concentration of particular nutrients or ions. HKs phosphorylate their cognate response regulator in the cytoplasm. Almost all of the prototypical HK characterised structurally are homo-dimeric, and consist of three modules [1,2]. The cytoplasmic region is a well-conserved kinase domain that has two sub-domains: the catalytic and ATP-binding domain (CA) and the Dimerisation and Histidine phosphotransfer domain (DHp), which phosphorylates its cognate response regulator. The HK controls the phosphorylation state of the RR, thereby modulating the RR DNA-binding capacity [1,2]

Methods

Results

Conclusion