Acta Crystallogr D Biol Crystallogr. 2001 Apr; 57(Pt 4): 602-4.

Preliminary crystallographic studies of EcTI, a serine proteinase inhibitor from Enterolobium contortisiliquum seeds.

Batista IF, Nonato MC, Bonfadini MR, Beltramini LM, Oliva ML, Sampaio MU, Sampaio CA, Garratt RC.

Departamento de BioquÃmica, Universidade Federal de SÃ£o Paulo (UNIFESP/EPM), Rua TrÃªs de Maio 100, CEP 04044-020 Sao Paulo SP, Brazil. [email protected]

Enterolobium contortisiliquum trypsin inhibitor (EcTI) belongs to the Kunitz family of plant inhibitors, which are widely distributed in nature, especially in plant seeds. EcTI is composed of two polypeptide chains with a total of 174 residues, homologous to other inhibitors from the same family. EcTI crystals, which were obtained with the acupuncture-gel technique, diffract to 2.0 A resolution and belong to space group P2(1), with unit-cell parameters a = 37.12, b = 38.42, c = 54.08 A, beta = 98.08 degrees. Molecular-replacement techniques using Erythrina caffra trypsin inhibitor (PDB code 1tie) as the search model indicate one monomer in the asymmetric unit. The secondary-structure content of EcTI was determined by circular dichroism spectroscopy, yielding values compatible with the expected topology.