Meulenbroek Elisabeth M, Thomassen Ellen A J, Pouvreau Laurice, Abrahams Jan Pieter, Gruppen Harry, Pannu Navraj S
Biophysical Structural Chemistry, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands.
Acta Crystallogr D Biol Crystallogr. 2012 Jul;68(Pt 7):794-9. doi: 10.1107/S090744491201222X. Epub 2012 Jun 15.
Potato serine protease inhibitor (PSPI) constitutes about 22% of the total amount of proteins in potato tubers (cv. Elkana), making it the most abundant protease inhibitor in the plant. PSPI is a heterodimeric double-headed Kunitz-type serine protease inhibitor that can tightly and simultaneously bind two serine proteases by mimicking the substrate of the enzyme with its reactive-site loops. Here, the crystal structure of PSPI is reported, representing the first heterodimeric double-headed Kunitz-type serine protease inhibitor structure to be determined. PSPI has a β-trefoil fold and, based on the structure, two reactive-site loops bearing residues Phe75 and Lys95 were identified.
马铃薯丝氨酸蛋白酶抑制剂（PSPI）约占马铃薯块茎（品种为埃尔卡纳）蛋白质总量的22%，使其成为该植物中含量最丰富的蛋白酶抑制剂。PSPI是一种异源二聚体双头库尼茨型丝氨酸蛋白酶抑制剂，它可以通过其反应位点环模拟酶的底物，紧密且同时结合两种丝氨酸蛋白酶。在此，报道了PSPI的晶体结构，这是首个被确定的异源二聚体双头库尼茨型丝氨酸蛋白酶抑制剂结构。PSPI具有β-三叶折叠结构，基于该结构，鉴定出了两个带有苯丙氨酸75和赖氨酸95残基的反应位点环。
