Structure and reaction mechanism analyses of enzymes in an alternative menaquinone biosynthetic patyway

2015 Fiscal Year Final Research Report

• Project/Area Number: 24780097
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Applied biochemistry
• Research Institution: Shinshu University
• Principal Investigator: ARAI Ryoichi 信州大学, 学術研究院繊維学系, 助教 (50344023)
• Project Period (FY): 2012-04-01 – 2016-03-31
• Keywords: メナキノン / ビタミンK / 生合成 / 酵素反応機構 / X線結晶構造解析 / MqnD / 高度好熱菌 / ピロリ菌

Outline of Final Research Achievements

An alternative biosynthetic pathway of menaquinone (vitamin K2) was found in some microorganisms including Streptomyces coelicolor and Thermus thermophilus. Since the pathogenic species such as Helicobacter pylori and Campylobacter jejuni also have essential enzymes in the alternative menaquinone biosynthetic pathway, the enzymes are attractive targets for the development of chemotherapeutics. Here we report the 1.5 angstrom crystal structure of the H145A variant of MqnD from T. thermophiles, complexed with its substrate. The substrate with ring-closing form was bound to the active-site pocket between the two domains, a large domain and a small domain. The His145Ala variant produces no enzymatic reaction, suggesting that His145 is an essential active residue as a catalytic base. Furthermore, we solved the crystal structure of MqnD complexed with the product, one of its reaction products. These results provide new insights into the enzymatic reaction mechanism of MqnD.

Free Research Field

構造生物学