title: New small proteinase inhibitors from Capsicum annuum seeds: Characterization, stability, spectroscopic analysis and a cDNA cloning.
abstract: Recent results from our laboratory have previously shown the purification of a small serine proteinase inhibitor (PI), named CaTI1, from Capsicum annuum seeds. This work demonstrated the characterization of CaTI now named CaTI1, and the identification of two other small serine PIs, named CaTI2 and CaTI3, also present in these seeds. CaTI1 presented molecular mass of 6 kDa and pI value of ∼9.0. CaTI1 inhibited both trypsin and chymotrypsin with inhibition constants (Ki and Ki') of 14 and 2.8 nM for trypsin and 4.3 and 0.58 nM for chymotrypsin, respectively. Circular dichroism analysis suggested the predominance of both disordered and β-strands regions in the secondary structure. CaTI1 presented striking physico-chemical stability. In an attempt to get the entire sequence of CaTI1 we found another PI called CaTI2. The discussion of this finding is in the main text. A degenerate primer was designed based on the sequence of trypsin inhibitor CaTI1 in an attempt to achieve the cloning of this PI. Surprisingly, the alignment of the predicted peptide derived from the cDNA with the protein database showed similarity with other C. annuun PIs, and thus it was called CaTI3.
authors.affiliation: Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense, Campos dos Goytacazes, 28015-602, Rio de Janeiro, Brazil.
authors.forename: Suzanna F F
authors.initials: SF
authors.lastname: Ribeiro
authors.forename: Kátia V S
authors.initials: KV
authors.lastname: Fernandes
authors.forename: Izabela S
authors.initials: IS
authors.lastname: Santos
authors.forename: Gabriel B
authors.initials: GB
authors.lastname: Taveira
authors.forename: André O
authors.initials: AO
authors.lastname: Carvalho
authors.forename: José Luiz S
authors.initials: JL
authors.lastname: Lopes
authors.forename: Leila M
authors.initials: LM
authors.lastname: Beltramini
authors.forename: Rosana
authors.initials: R
authors.lastname: Rodrigues
authors.forename: Ilka M
authors.initials: IM
authors.lastname: Vasconcelos
authors.forename: Maura
authors.initials: M
authors.lastname: Da Cunha
authors.forename: Gonçalo A
authors.initials: GA
authors.lastname: Souza-Filho
authors.forename: Valdirene M
authors.initials: VM
authors.lastname: Gomes
mesh_terms: D000595:Amino Acid Sequence; D002212:Capsicum; D003001:Cloning, Molecular; D018076:DNA, Complementary; D008969:Molecular Sequence Data; D012639:Seeds / Q000737:chemistry; D014357:Trypsin / Q000378:metabolism; D014361:Trypsin Inhibitors / Q000737:chemistry
chemical_list: D018076:DNA, Complementary; D014361:Trypsin Inhibitors; D014357:Trypsin