Rice Elena A, Bannon Gary A, Glenn Kevin C, Jeong Soon Seog, Sturman Eric J, Rydel Timothy J
Monsanto Company, 800 North Lindbergh Boulevard, St. Louis, MO 63167, USA.
Arch Biochem Biophys. 2008 Dec 15;480(2):111-21. doi: 10.1016/j.abb.2008.09.018. Epub 2008 Oct 7.
The lysine insensitive Corynebacterium glutamicum dihydrodipicolinate synthase enzyme (cDHDPS) was recently successfully introduced into maize plants to enhance the level of lysine in the grain. To better understand lysine insensitivity of the cDHDPS, we expressed, purified, kinetically characterized the protein, and solved its X-ray crystal structure. The cDHDPS enzyme has a fold and overall structure that is highly similar to other DHDPS proteins. A noteworthy feature of the active site is the evidence that the catalytic lysine residue forms a Schiff base adduct with pyruvate. Analyses of the cDHDPS structure in the vicinity of the putative binding site for S-lysine revealed that the allosteric binding site in the Escherichia coli DHDPS protein does not exist in cDHDPS due to three non-conservative amino acids substitutions, and this is likely why cDHDPS is not feedback inhibited by lysine.
赖氨酸不敏感的谷氨酸棒杆菌二氢吡啶二羧酸合酶（cDHDPS）最近成功导入玉米植株，以提高籽粒中的赖氨酸水平。为了更好地理解cDHDPS对赖氨酸的不敏感性，我们对该蛋白进行了表达、纯化、动力学表征，并解析了其X射线晶体结构。cDHDPS酶的折叠和整体结构与其他二氢吡啶二羧酸合酶蛋白高度相似。活性位点的一个显著特征是有证据表明催化赖氨酸残基与丙酮酸形成了席夫碱加合物。对cDHDPS结构中假定的S-赖氨酸结合位点附近区域的分析表明，由于三个非保守氨基酸取代，大肠杆菌二氢吡啶二羧酸合酶蛋白中的变构结合位点在cDHDPS中不存在，这可能就是cDHDPS不受赖氨酸反馈抑制的原因。
