Open AccessPurification, crystallization and X‐ray characterization of a Kunitz‐type trypsin inhibitor protein from the seeds of chickpea ( Cicer arietinum )
Author(s) -
Sharma Urvashi,
Suresh C. G.
Publication year - 2011
Publication title -
acta crystallographica section f
Language(s) - English
Resource type - Journals
ISSN - 1744-3091
DOI - 10.1107/s1744309111015338
Subject(s) - trypsin , orthorhombic crystal system , trypsin inhibitor , crystallization , chemistry , crystallography , resolution (logic) , molecular mass , chromatography , crystal structure , enzyme , biochemistry , organic chemistry , artificial intelligence , computer science
A Kunitz‐type trypsin inhibitor protein (CPTI) purified from chickpea seeds was estimated to have a molecular mass of 18 kDa on SDS–PAGE. The IC 50 value of CPTI was determined to be 2.5 µg against trypsin. The inhibitory activity of CPTI is 114 TIU (trypsin inhibitory units) per milligram of protein, which is high compared with those of other known Kunitz‐type trypsin inhibitors from legumes. CPTI crystallized in three different orthorhombic crystal forms: P 2 1 2 1 2 form A, P 2 1 2 1 2 form B and P 2 1 2 1 2 1 . The crystals of P 2 1 2 1 2 form A , with unit‐cell parameters a = 37.2, b = 41.2, c = 104.6 Å, diffracted to 2.0 Å resolution at the home source and to 1.4 Å on beamline BM14 at the ESRF. Data were also collected from crystals grown in the presence of iodine. The Matthews coefficient for these crystals was calculated to be 2.37 Å 3 Da −1 , corresponding to a solvent content of 42%. The other two crystal forms ( P 2 1 2 1 2 form B and P 2 1 2 1 2 1 ) diffracted comparatively poorly.