Abstract
An uncertain intron of 87 bp within the cDNA sequences of arrowhead proteinase inhibitorsA and B was clarified. By site-directed mutation with either a stop codon inside theuncertain intron or mutated codons at both its 5' and 3' ends, it was proved that there wasneither a translation intron nor a protein intron present in the cDNA sequences ofproteinase inhibitors A and B. The primary structure of inhibitor B was then reexaminedby mass spectrometry molecular weight determination and partial amino acid sequencing. A 38 residue peptide was derived by degradation of inhibitor B with lysylendopeptidase, and purified, which was not found in the previous work, and its N-terminal part was noneother than the missed 29 residue peptide encoded by the uncertain intron. The 38 residuepeptide was very hydrophobic, while the 29 residue peptide it included was even morehydrophobic. The N-terminal part of the missed peptide was also aligned within aBrCN-degraded fragment of the inhibitor. In this paper the cause of the overlooking of this29 residue peptide in the previous work and some unexpected problems which arose duringthe former sequence analysis are explained.
