Hamada K, Hata Y, Katsuya Y, Hiramatsu H, Fujiwara T, Katsube Y
Faculty of Science, Shimane University.
J Biochem. 1996 May;119(5):844-51. doi: 10.1093/oxfordjournals.jbchem.a021320.
The crystal structure of Serratia protease from Serratia sp. E-15 was solved by the single isomorphous replacement method supplemented with anomalous scattering effects from both the Zn atom in the native crystal and the Sm atom in the derivative crystal, and refined at 2.0 A resolution to a crystallographic R-factor of 0.194. The enzyme consists of N-terminal catalytic and C-terminal beta-sandwich domains, as observed in alkaline protease from Pseudomonas aeruginosa IFO3080. The catalytic domain with a five-stranded antiparallel beta-sheet and five alpha-helices shares a basically common folding topology with those of other zinc metalloendoproteases. The catalytic zinc ion at the bottom of the active site cleft is ligated by His176, His180, His186, Tyr216, and a water molecule in a distorted trigonalbipyramidal manner. The C-terminal domain is a beta-strand-rich domain containing eighteen beta-strands and a short alpha-helix, and has seven Ca2+ ions bound to calcium binding loops. An unusual beta-sheet coil motif is observed in this domain, where the beta-strands and calcium binding loops are alternately incorporated into an elliptical right-handed spiral so as to form a two-layer untwisted beta-sandwich structure. The Ca2+ ions in the C-terminal domain seem to be very important for the folding and stability of the beta-sheet coil structure.
通过单同晶置换法并结合天然晶体中的锌原子和衍生晶体中的钐原子的反常散射效应，解析了粘质沙雷氏菌E-15菌株的粘质沙雷氏菌蛋白酶的晶体结构，并在2.0埃分辨率下进行精修，使其晶体学R因子达到0.194。该酶由N端催化结构域和C端β-折叠结构域组成，这与铜绿假单胞菌IFO3080的碱性蛋白酶情况相同。具有五股反平行β-折叠和五个α-螺旋的催化结构域与其他锌金属内蛋白酶的催化结构域具有基本相同的折叠拓扑结构。活性位点裂隙底部的催化锌离子以扭曲的三角双锥方式与His176、His180、His186、Tyr216和一个水分子配位。C端结构域是一个富含β-链的结构域，包含18条β-链和一个短α-螺旋，并有7个Ca2+离子与钙结合环结合。在该结构域中观察到一种不寻常的β-折叠-螺旋基序，其中β-链和钙结合环交替纳入椭圆形右手螺旋，从而形成两层未扭曲的β-折叠结构。C端结构域中的Ca2+离子似乎对β-折叠-螺旋结构的折叠和稳定性非常重要。
