Zinc-, cobalt- and iron-chelated forms of adenylate kinase from the Gram-negative bacterium Desulfovibrio

详细信息    查看全文

• 作者：Anna V. Kladova ; Olga Yu. Gavel ; Galina G. Zhadan ; Manuel G. Roig ; Valery L. Shnyrov ; Sergey A. Bursakov
• 关键词：Adenylate kinase ; Thermostability ; Desulfovibrio gigas
• 刊名：International Journal of Biological Macromolecules
• 出版年：2009
• 出版时间：1 December 2009
• 年：2009
• 卷：45
• 期：5
• 页码：524-531
• 全文大小：297 K

文摘

Adenylate kinase (AK) from the sulphate-reducing bacterium Desulfovibrio gigas (AK) has been characterized earlier as a Co²⁺/Zn²⁺-containing enzyme, which is an unusual characteristic for adenylate kinases from Gram-negative bacteria, in which these enzymes are normally devoid of metal ions. AK was overexpressed in E. coli and homogeneous Co²⁺-, Zn²⁺- and Fe²⁺-forms of the enzyme were obtained under in vivo conditions. Their structural stability and spectroscopic and kinetic properties were compared. The thermal denaturation of Co²⁺- and Zn²⁺-forms of AK was studied as a cooperative two-state process, sufficiently reversible at pH 10, which can be correctly interpreted in terms of a simple two-state thermodynamic model. In contrast, the thermally induced denaturation of Fe²⁺-AK is irreversible and strongly dependent upon the scan rate, suggesting that this process is under kinetic control. Practically identical contents of secondary-structure elements were found for all the metal-chelated-forms of AK upon analysis of circular dichroism data, while their tertiary structures were significantly different. The peculiar tertiary structure of Fe²⁺-AK, in contrast to Co²⁺- and Zn²⁺-AK, and the consequent changes in the physico-chemical and enzymatic properties of the enzyme are discussed.