Article

Salt-driven Equilibrium Between two Conformations in the HAMP Domain from Natronomonas Pharaonis: The Language of Signal Transfer?

Fachbereich Physik, Universität Osnabrück, Barbarastrasse 7, 49076 Osnabrück, Germany.
Journal of Biological Chemistry (Impact Factor: 4.57). 09/2008; 283(42):28691-701. DOI: 10.1074/jbc.M801931200
Source: PubMed

ABSTRACT

HAMP domains (conserved in histidine kinases, adenylyl cyclases, methyl-accepting chemotaxis proteins, and phosphatases) perform their putative function as signal transducing units in diversified environments in a variety of protein families. Here the conformational changes induced by environmental agents, namely salt and temperature, on the structure and function of a HAMP domain of the phototransducer from Natronomonas pharaonis (NpHtrII) in complex with sensory rhodopsin II (NpSRII) were investigated by site-directed spin labeling electron paramagnetic resonance. A series of spin labeled mutants were engineered in NpHtrII157, a truncated analog containing only the first HAMP domain following the transmembrane helix 2. This truncated transducer is shown to be a valid model system for a signal transduction domain anchored to the transmembrane light sensor NpSRII. The HAMP domain is found to be engaged in a "two-state" equilibrium between a highly dynamic (dHAMP) and a more compact (cHAMP) conformation. The structural properties of the cHAMP as proven by mobility, accessibility, and intra-transducer-dimer distance data are in agreement with the four helical bundle NMR model of the HAMP domain from Archaeoglobus fulgidus.

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Available from: Johann P Klare, Nov 10, 2015
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    • "The resulting transient EPR spectroscopy data for the HAMP domain shows a pattern of light-dependent local immobilization. This is in agreement with the structural transition described in the two-state model[11,22]and with the dynamic bundle model[7,19,24,25], suggesting a unified view of HAMP domain signaling via switching of conformation and dynamics.of Physics, University of Osnabrück, Barbarastr. "
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    ABSTRACT: HAMP domains are widely abundant signaling modules. The putative mechanism of their function comprises switching between two distinct states. To unravel these conformational transitions, we apply site-directed spin labeling and time-resolved EPR spectroscopy to the phototactic receptor/transducer complex NpSRII/NpHtrII. We characterize the kinetic coupling of NpHtrII to NpSRII along with the activation period of the transducer and follow the transient conformational signal. The observed transient shift towards a more compact state of the HAMP domain upon light-activation agrees with structure-based calculations. It thereby validates the two modeled signaling states and integrates the domain's dynamics into the current model.
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    • "As for phototactic signal transducers, it was first proposed that the HAMP domain of NpHtrII transduces the signal via switching between a compact and a highly dynamic states [14], [15]. Later, the fluorescent labeling studies revealed that the helices AS1 and AS2 move in opposite directions during signal transduction [16]. "
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    ABSTRACT: HAMP domain is a ubiquitous module of bacterial and archaeal two-component signaling systems. Considerable progress has been made recently in studies of its structure and conformational changes. However, the mechanism of signal transduction through the HAMP domain is not clear. It remains a question whether all the HAMPs have the same mechanism of action and what are the differences between the domains from different protein families. Here, we present the results of unbiased molecular dynamics simulations of the HAMP domain from the archaeal phototaxis signal transducer NpHtrII. Two distinct conformational states of the HAMP domain are observed, that differ in relative position of the helices AS1 and AS2. The longitudinal shift is roughly equal to a half of an α-helix turn, although sometimes it reaches one full turn. The states are closely related to the position of bulky hydrophobic aminoacids at the HAMP domain core. The observed features are in good agreement with recent experimental results and allow us to propose that the states detected in the simulations are the resting state and the signaling state of the NpHtrII HAMP domain. To the best of our knowledge, this is the first observation of the same HAMP domain in different conformations. The simulations also underline the difference between AMBER ff99-SB-ILDN and CHARMM22-CMAP forcefields, as the former favors the resting state and the latter favors the signaling state.
    Full-text · Article · Jul 2013 · PLoS ONE
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    • "A more detailed SDSL EPR study on the first NpHtrII HAMP domain investigating the structural and dynamic features in dependency of salt concentration (Figure 4B) and temperature revealed that the HAMP domain is engaged in a " two-state " equilibrium between a highly dynamic (dHAMP) and a compact (cHAMP) conformation (Döbber et al., 2008) (Figure 5). The structural properties of the cHAMP conformation as proven by mobility, accessibility, and intra-transducer-dimer distance data were found to be in agreement with the four helical bundle NMR model of the HAMP domain from Archaeoglobus fulgidus. "
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    ABSTRACT: Archaeal photoreceptors, together with their cognate transducer proteins, mediate phototaxis by regulating cell motility through two-component signal transduction pathways. This sensory pathway is closely related to the bacterial chemotactic system, which has been studied in detail during the past 40 years. Structural and functional studies applying site-directed spin labelling and electron paramagnetic resonance spectroscopy on the sensory rhodopsin II/transducer (NpSRII/NpHtrII) complex of Natronomonas pharaonis have yielded insights into the structure, the mechanisms of signal perception, the signal transduction across the membrane and provided information about the subsequent information transfer within the transducer protein towards the components of the intracellular signalling pathway. Here, we provide an overview about the findings of the last decade, which, combined with the wealth of data from research on the Escherichia coli chemotaxis system, served to understand the basic principles microorganisms use to adapt to their environment. We document the time course of a signal being perceived at the membrane, transferred across the membrane and, for the first time, how this signal modulates the dynamic properties of a HAMP domain, a ubiquitous signal transduction module found in various protein classes.
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