Reference "Structure of the bifunctional inhibitor of trypsin and alpha-amylase from ragi seeds at 2.9 A resolution"

Reference ID

9542

Title

Structure of the bifunctional inhibitor of trypsin and alpha-amylase from ragi seeds at 2.9 A resolution

Source

Acta Crystallogr D Biol Crystallogr, 1999, vol. 55 ( Pt 1), pp. 25-30

Authors (3)

Gourinath-S	Srinivasan-A
Singh-T-P

Abstract

The crystal structure of a bifunctional inhibitor of alpha-amylase and trypsin
from the seeds of ragi (Indian finger millet, Eleusine coracana Gaertneri) has
been determined by an X-ray diffraction method. The inhibitor consists of 122
amino acids with five disulfide bridges and belongs to the plant alpha-amylase/trypsin-
inhibitor family. This is the first crystal structure determination of a member
of this family. The protein, purified from the seeds of ragi, has a molecular
mass of 13300 Da with a pI of 10.3. Crystals were grown by a microdialysis
method using ammonium sulfate as precipitant. The improved purification
protocol and the modified crystallization conditions enabled reproducible
growth of the crystals. The cell parameters are a = 41. 2, b = 47.4, c = 55.9
A. The intensity data were collected to 2.9 A resolution, and the crystal
structure was determined using the molecular-replacement method. The structure
was refined using the X-PLOR and CCP4 program packages to a conventional R
factor of 21%. The structure contains four alpha-helices between residues 19-
29, 37-51, 56-65 and 90-95, and two short antiparallel beta-strands between
residues 67-70 and 73-75.