Soisson Stephen M, Patel Sangita B, Abeywickrema Pravien D, Byrne Noel J, Diehl Ronald E, Hall Dawn L, Ford Rachael E, Reid John C, Rickert Keith W, Shipman Jennifer M, Sharma Sujata, Lumb Kevin J
Global Structural Biology, Merck Research Laboratories, P,O, Box 4, West Point, PA 19486, USA.
BMC Struct Biol. 2010 Jun 11;10:16. doi: 10.1186/1472-6807-10-16.
The unique S28 family of proteases is comprised of the carboxypeptidase PRCP and the aminopeptidase DPP7. The structural basis of the different substrate specificities of the two enzymes is not understood nor has the structure of the S28 fold been described.
The experimentally phased 2.8 A crystal structure is presented for human PRCP. PRCP contains an alpha/beta hydrolase domain harboring the catalytic Asp-His-Ser triad and a novel helical structural domain that caps the active site. Structural comparisons with prolylendopeptidase and DPP4 identify the S1 proline binding site of PRCP. A structure-based alignment with the previously undescribed structure of DPP7 illuminates the mechanism of orthogonal substrate specificity of PRCP and DPP7. PRCP has an extended active-site cleft that can accommodate proline substrates with multiple N-terminal residues. In contrast, the substrate binding groove of DPP7 is occluded by a short amino-acid insertion unique to DPP7 that creates a truncated active site selective for dipeptidyl proteolysis of N-terminal substrates.
The results define the structure of the S28 family of proteases, provide the structural basis of PRCP and DPP7 substrate specificity and enable the rational design of selective PRCP modulators.
独特的S28蛋白酶家族由羧肽酶PRCP和氨肽酶DPP7组成。两种酶不同底物特异性的结构基础尚不清楚，S28折叠的结构也未被描述。
给出了人PRCP的2.8埃晶体结构，该结构通过实验确定了相位。PRCP包含一个带有催化性天冬氨酸-组氨酸-丝氨酸三联体的α/β水解酶结构域和一个覆盖活性位点的新型螺旋结构域。与脯氨酰内肽酶和DPP4的结构比较确定了PRCP的S1脯氨酸结合位点。与之前未描述的DPP7结构进行基于结构的比对，阐明了PRCP和DPP7正交底物特异性的机制。PRCP具有一个延伸的活性位点裂隙，可容纳带有多个N端残基的脯氨酸底物。相比之下，DPP7的底物结合凹槽被DPP7特有的短氨基酸插入所封闭，从而形成了一个对N端底物的二肽基蛋白水解具有选择性的截短活性位点。
这些结果确定了S28蛋白酶家族的结构，提供了PRCP和DPP7底物特异性的结构基础，并有助于合理设计选择性PRCP调节剂。
