Halophilic Adaptation: Novel Solvent Protein Interactions Observed in the 2.9 and 2.6 Å Resolution Structures of the Wild Type and a Mutant of Malate Dehydrogenase from Haloarcula marismortui

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• 作者：Sté ; phane B. Richard ; Dominique Madern ; Elsa Garcin ; and Giuseppe Zaccai
• 刊名：Biochemistry
• 出版年：2000
• 出版时间：February 8, 2000
• 年：2000
• 卷：39
• 期：5
• 页码：992 - 1000
• 全文大小：987K
• 年卷期：v.39,no.5(February 8, 2000)
• ISSN：1520-4995

文摘

Previous biophysical studies of tetrameric malate dehydrogenase from the halophilic archaeonHaloarcula marismortui (Hm MalDH) have revealed the importance of protein-solvent interactions forits adaptation to molar salt conditions that strongly affect protein solubility, stability, and activity, ingeneral. The structures of the E267R stability mutant of apo (-NADH) Hm MalDH determined to 2.6 Åresolution and of apo (-NADH) wild type Hm MalDH determined to 2.9 Å resolution, presented here,highlight a variety of novel protein-solvent features involved in halophilic adaptation. The tetramer appearsto be stabilized by ordered water molecule networks and intersubunit complex salt bridges "locked" in bybound solvent chloride and sodium ions. The E267R mutation points into a central ordered water cavity,disrupting protein-solvent interactions. The analysis of the crystal structures showed that halophilicadaptation is not aimed uniquely at "protecting" the enzyme from the extreme salt conditions, as mayhave been expected, but, on the contrary, consists of mechanisms that harness the high ionic concentrationin the environment.