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Molecular mechanism of enzyme inhibition: prediction of the three-dimensional structure of the dimeric trypsin inhibitor from Leucaena leucocephala by homology modelling.

Abstract：

:Serine proteinase inhibitors are widely distributed in nature and inhibit the activity of enzymes like trypsin and chymotrypsin. These proteins interfere with the physiological processes such as germination, maturation and form the first line of defense against the attack of seed predator. The most thoroughly examined plant serine proteinase inhibitors are found in the species of the families Leguminosae, Graminae, and Solanaceae. Leucaena leucocephala belongs to the family Leguminosae. It is widely used both as an ornamental tree as well as cattle food. We have constructed a three-dimensional model of a serine proteinase inhibitor from L. leucocephala seeds (LTI) complexed with trypsin. The model was built based on its comparative homology with soybean trypsin inhibitor (STI) using the program, MODELLER6. The quality of the model was assessed stereochemically by PROCHECK. LTI shows structural features characteristic of the Kunitz type trypsin inhibitor and shows 39% residue identity with STI. LTI consists of 172 amino acid residues and is characterized by two disulfide bridges. The protein is a dimer with the two chains being linked by a disulfide bridge. Despite the high similarity in the overall tertiary structure, significant differences exist at the active site between STI and LTI. The present study aims at analyzing these interactions based on the available amino acid sequences and structural data. We have also studied some functional sites such as phosphorylation, myristoylation, which can influence the inhibitory activity or complexation with other molecules. Some of the differences observed at the active site and functional sites can explain the unique features of LTI.

journal_name

Biochem Biophys Res Commun

journal_title

Biochemical and biophysical research communications

authors

Sattar R,Ali SA,Kamal M,Khan AA,Abbasi A

doi

10.1016/j.bbrc.2003.12.177

subject

Has Abstract

pub_date

2004-02-13 00:00:00

pages

755-65

issue

eissn

0006-291X

issn

1090-2104

pii

S0006291X03027918

journal_volume

314

pub_type

杂志文章

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Molecular mechanism of enzyme inhibition: prediction of the three-dimensional structure of the dimeric trypsin inhibitor from Leucaena leucocephala by homology modelling.