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Molecular Mechanism of Dimerization of Bowman-Birk Inhibitors: Pivotal Role Of Asp76 in the Dimerzation

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JBC-15-04
 
Title Molecular Mechanism of Dimerization of Bowman-Birk Inhibitors: Pivotal Role Of Asp76 in the Dimerzation
 
Creator Pradeep, Kumar
Appu Rao, A. G.
Sridhar, Hariharaputran
Chandra, Nagasuma
Gowda, Lalitha R.
 
Subject 29 Protein Chemistry
22 Legumes-Pulses
 
Description Horsegram (Dolichos biflorus), a protein-rich leguminous
pulse, is a crop native to Southeast Asia and tropical
Africa. The seeds contain multiple forms of Bowman-
Birk type inhibitors. The major inhibitor HGI-III,
from the native seed with 76 amino acid residues exists
as a dimer. The amino acid sequence of three isoforms of
Bowman-Birk inhibitor from germinated horsegram,
designated as HGGI-I, HGGI-II, and HGGI-III, have been
obtained by sequential Edman analyses of the pyridylethylated inhibitors and peptides derived therefrom by enzymatic and chemical cleavage. The HGGIs are monomers,
comprising of 66, 65, and 60 amino acid residues,
respectively. HGGI-III from the germinated seed differs
from the native seed inhibitor in the physiological deletion of a dodecapeptide at the amino terminus and a
tetrapeptide, -SHDD, at the carboxyl terminus. The
study of the state of association of HGI-III, by size-exclusion chromatography and SDS-PAGE in the presence
of 1 mM ZnCl2, has revealed the role of charged interactions in the monomer 7 dimer equilibria. Chemical
modification studies of Lys and Arg have confirmed the
role of charge interactions in the above equilibria.
These results support the premise that a unique interaction,which stabilizes the dimer, is the cause of selfassociation in the inhibitors. This interaction in HGI-III involves the _-amino group of the Lys24 (P1 residue) at
the first reactive site of one monomer and the carboxyl
of an Asp76 at the carboxyl terminus of the second monomer.
Identification of the role of these individual
amino acids in the structure and stability of the dimer
was accomplished by chemical modifications, multiple
sequence alignment of legume Bowman-Birk inhibitors,
and homology modeling. The state of association may
also influence the physiological and functional role of
these inhibitors.
 
Date 2004-07
 
Type Article
PeerReviewed
 
Format application/pdf
 
Language en
 
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Identifier http://ir.cftri.com/1626/1/JBC_279_30425_-_30432_2004.pdf
Pradeep, Kumar and Appu Rao, A. G. and Sridhar, Hariharaputran and Chandra, Nagasuma and Gowda, Lalitha R. (2004) Molecular Mechanism of Dimerization of Bowman-Birk Inhibitors: Pivotal Role Of Asp76 in the Dimerzation. Journal of Biological Chemistry, 279 (29). pp. 30425-30432.