Reference "Structure of the bifunctional inhibitor of trypsin and alpha-amylase from ragi seeds at 2.2 A resolution"

Reference ID

9543

Title

Structure of the bifunctional inhibitor of trypsin and alpha-amylase from ragi seeds at 2.2 A resolution

Source

Acta Crystallogr D Biol Crystallogr, 2000, vol. 56 ( Pt 3), pp. 287-293

Authors (5)

Gourinath-S	Alam-N
Srinivasan-A	Betzel-C
Singh-T-P

Abstract

The crystal structure of a bifunctional inhibitor of alpha-amylase and trypsin
(RATI) from ragi seeds (Indian finger millet, Eleusine coracana Gaertneri) has
been determined by X-ray diffraction at 2.2 A resolution. The inhibitor consists
of 122 amino acids, with five disulfide bridges, and belongs to the plant alpha-
amylase/trypsin inhibitor family. The crystals were grown by the microdialysis
method using ammonium sulfate as a precipitating agent. The structure was
determined by the molecular-replacement method using as models the structures of
Corn Hageman factor inhibitor (CHFI) and of RATI at 2.9 A resolution determined
previously. It has been refined to an R factor of 21.9%. The structure shows an
r.m.s. deviation for C(alpha) atoms of 2.0 A compared with its own NMR
structure, whereas the corresponding value compared with CHFI is found to be 1.4
A. The r.m.s. difference for C(alpha) atoms when compared with the same protein
in the structure of the complex with alpha-amylase is 0.7 A. The conformations
of trypsin-binding loop and the alpha-amylase-binding N-terminal region were
also found to be similar in the crystal structures of native RATI and its
complex with alpha-amylase. These regions differed considerably in the NMR
structure.