Structural basis for cold adaptation: Sequence, biochemical properties, and crystal structure of malate dehydrogenase from a psychrophile Aquaspirillium arcticum

Sun Yong Kim, Kwang Yeon Hwang, Sung Hou Kim, Ha Chin Sung, Ye Sun Han, Yunje Cho

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Aquaspillium arcticum is a psychrophilic bacterium that was isolated from arctic sediment and grows optimally at 4°C. We have cloned, purified, and characterized malate dehydrogenase from A. arcticum (Aa MDH). We also have determined the crystal structures of apo-Aa MDH, Aa MDH·NADH binary complex, and Aa MDH·NAD·oxaloacetate ternary complex at 1.9-, 2.1-, and 2.5-Å resolutions, respectively. The Aa MDH sequence is most closely related to the sequence of a thermophilic MDH from Thermus flavus (Tf MDH), showing 61% sequence identity and over 90% sequence similarity. Stability studies show that Aa MDH has a half-life of 10 min at 55°C, whereas Tf MDH is fully active at 90°C for 1 h. Aa MDH shows 2-3-fold higher catalytic efficiency compared with a mesophilic or a thermophilic MDH at the temperature range 4- 10°C. Structural comparison of Aa MDH and Tf MDH suggests that the increased relative flexibility of active site residues, favorable surface charge distribution for substrate and cofactor, and the reduced intersubunit ion pair interactions may be the major factors for the efficient catalytic activity of Aa MDH at low temperatures.

Original languageEnglish
Pages (from-to)11761-11767
Number of pages7
JournalJournal of Biological Chemistry
Issue number17
Publication statusPublished - 1999 Apr 23
Externally publishedYes


ASJC Scopus subject areas

  • Biochemistry

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