Doebber Meike, Bordignon Enrica, Klare Johann P, Holterhues Julia, Martell Swetlana, Mennes Nadine, Li Lin, Engelhard Martin, Steinhoff Heinz-Jürgen
Fachbereich Physik, Universität Osnabrück, Barbarastrasse 7, 49076 Osnabrück, Germany.
J Biol Chem. 2008 Oct 17;283(42):28691-701. doi: 10.1074/jbc.M801931200. Epub 2008 Aug 11.
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.
HAMP结构域（在组氨酸激酶、腺苷酸环化酶、甲基接受趋化蛋白和磷酸酶中保守）在多种蛋白质家族的不同环境中作为信号转导单元发挥其假定功能。在此，通过定点自旋标记电子顺磁共振研究了环境因素，即盐和温度，对来自嗜盐碱红菌（NpHtrII）的光感受器与感官视紫红质II（NpSRII）复合物中HAMP结构域的结构和功能所诱导的构象变化。在NpHtrII157中构建了一系列自旋标记突变体，NpHtrII157是一个截短类似物，仅包含跨膜螺旋2之后的第一个HAMP结构域。该截短的光感受器被证明是锚定在跨膜光传感器NpSRII上的信号转导结构域的有效模型系统。发现HAMP结构域在高度动态（dHAMP）和更紧凑（cHAMP）构象之间处于“双态”平衡。通过迁移率、可及性和跨光感受器二聚体距离数据证明的cHAMP的结构特性与来自嗜热栖热菌的HAMP结构域的四螺旋束核磁共振模型一致。
