2009年9月1日，清华大学施一公教授团队在美国PNAS杂志发表了题为“Cleavage of RseA by RseP requires a carboxyl-terminal hydrophobic amino acid following DegS cleavage”的文章。
细胞外环境变化会通过一系列的信号转导通路最终影响细胞内部的代谢水平，受控膜内蛋白水解（Regulated intramembrane proteolysis,RIP）是近年发现的一种调节膜蛋白内外信号传导的机制。S2P是一种膜整合金属蛋白酶，其底物也是膜蛋白。S2P切割膜底物，使之释放被细胞膜束缚住的信号分子，从而将信号传导至细胞核中。但是令人费解的是，S2P对底物的水解必须依赖另一种蛋白酶S1P对底物进行第一步切割之后才能发挥作用，这其中的机理尚不明确。
施一公教授领导的清华团队在9月初的《美国科学院院刊》（PNAS）发表文章，通过生物化学和结构生物学的手段对这一问题进行了解答，发现底物被S1P水解后暴露出的C端氨基酸对S2P的活性的调节发挥了重大的作用。本篇文章被选为此期杂志的封面介绍文章，美国西南医学中心神经生物系的两位科学家为此研究成果撰写的一篇评论同时发表在该杂志上，对这项工作进行高度赞誉，认为它为理解包括与老年痴呆症密切相关的gamma-Secretase在内的受控膜内蛋白水解的调节机理作出了重要突破。
值得一提的是，此工作在施一公老师和王佳伟老师的指导下，全部为清华大学一年级的研究生和高年级本科生完成。（生物谷Bioon.com）
生物谷推荐原始出处：
PNAS September 1, 2009 vol. 106 no. 35 14837-14842
Cleavage of RseA by RseP requires a carboxyl-terminal hydrophobic amino acid following DegS cleavage
Xiaochun Lia, Boyuan Wangb, Lihui Fenga, Hui Kanga, Yang Qia, Jiawei Wanga and Yigong Shia,b,1
aMinistry of Education Protein Science Laboratory and Center for Structural Biology, Department of Biological Sciences and Biotechnology, and
bSchool of Medicine, Tsinghua University, Beijing 100084, China
Regulated intramembrane proteolysis (RIP) by the Site-2 protease (S2P) results in the release of a transmembrane signaling protein. Curiously, however, S2P cleavage must be preceded by the action of the Site-1 protease (S1P). To decipher the underlying mechanism, we reconstituted sequential, in vitro cleavages of the Escherichia coli transmembrane protein RseA by DegS (S1P) and RseP (S2P). After DegS cleavage, the newly exposed carboxyl-terminal residue Val-148 of RseA plays an essential role for RseP cleavage, and its mutation to charged or dissimilar amino acids crippled the Site-2 cleavage. By contrast, the identity of residues 146 and 147 of RseA has no impact on Site-2 cleavage. These results explain why Site-1 cleavage must precede Site-2 cleavage. Structural analysis reveals that the putative peptide-binding groove in the second, but not the first, PDZ domain of RseP is poised for binding to a single hydrophobic amino acid. These observations suggest that after DegS cleavage, the newly exposed carboxyl terminus of RseA may facilitate Site-2 cleavage through direct interaction with the PDZ domain.
