Identification and cloning of a trypsin inhibitor from skin secretions of Chinese red-belly toad Bombina maxima.
A novel trypsin inhibitor was identified and purified from skin secretions of Chinese red-belly toad Bombina maxima. The partial N-terminal 29 amino acid residues of the peptide, named BMTI, were determined by automated Edman degradation. This allowed the cloning of a full-length cDNA encoding BMTI from a cDNA library prepared from the toad skin. The deduced complete amino acid sequence of BMTI indicates that mature BMTI is composed of 60 amino acids. A FASTA search in the databanks revealed that BMTI exhibits 81.7% sequence identity with BSTI, a trypsin/thrombin inhibitor from European toad Bombina bombina skin secretions. Sequence differences between BMTI and BSTI were due to 11 substitutions at positions 2, 9, 25, 27, 36-37, 39, 41-42, 50 and 56. BMTI potently inhibited trypsin with a K(i) value of 0.06 microM, similar to that of BSTI. However, unlike BSTI, which also inhibited thrombin with a K(i) value of 1 microM, no inhibitory effect of BMTI on thrombin was observed under the assay conditions.
Lai
Ren
R
Department of Animal Toxinology, Kunming Institute of Zoology, Chinese Academy of Sciences, 32 East Jiao Chang Road, Kunming 650223, Yunnan, PR China.
Liu
Hen
H
Lee
Wen Hui
WH
Zhang
Yun
Y
D000595:Amino Acid Sequence; D029845:Amphibian Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D000818:Animals; D001001:Anura / Q000235:genetics; D001483:Base Sequence; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003001:Cloning, Molecular; D008969:Molecular Sequence Data; D011506:Proteins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000378:metabolism; D012867:Skin / Q000737:chemistry* / Q000378:metabolism*; D014361:Trypsin Inhibitors / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification* / Q000378:metabolism
D029845:Amphibian Proteins; C101288:BSTI protein, Bombina bombina; D011506:Proteins; D014361:Trypsin Inhibitors; D012697:Serine Endopeptidases