Structural And Functional Stduy On CPI And GP73

(1)Cystatin is a type of cysteine protease inhibitor(CPI).It has been found to express in many species such as animal,plant,and microbe.The cystatin superfamily is composed of stefin,cystatin and kininogen.Their function mainly through the regulation of their target proteases,consisting of two types:C1(papin)and C13(legumain).Al-CPI and Hp-CPI are from Ascaris lumbricoides and Heligmosomoides polygyrus,respectively.They not only act on the parasite cysteine proteases in their development,but also have effect on the host proteases and regulate the immune response to facilitate the escaping from the host immune action.We determined three crystal structures of Al-CPI,two of which are dimer structures,and one is a monomer structure.From the comparison of the three structures,we observe changes not only in L1(becoming a ?L strucuture),but also in L2 in the dimerization process,resulting in the movement of the activity segment residues(PW).This explains the loss of the inhibitory activity of Al-CPI dimer.We also propose two characteristics of parasite cystatin structure:much tighter core and more open activity segment.These may come from the evolution of parasite.(?)GOLPH ?,also known as GOLM I,is a trans-membrane protein located in Golgi.GOLPH II was first isolated and identified from hepatitis macrophages by Kladney et al.The GOLPH II gene of human is located in chromosome 9.GOLPH ?is composed of 401amino acid residues.Its theoretical molecular weight is 45333.23Da and pI is 4.71.Since it is an acidic and glycosylated protein,it appears to be 73kD on SDS-PAGE,therefore it is also called GP73.GP73 is expressed in epithelial cells of many human tissues.GP73 is not or rarely expressed in human normal hepatocytes;However,the expression of GP73 is significantly up regulated in liver disease patients.This character potentially provides GP73 as a biomarker.In this study,we focus on xenopus GP73(xGP73)and human GP73(hGP73).We aim to obtain the structure of GP73and to help understand its function with the structure information.This will also provide structural basis for GP73 as a biomarker.