J. Biol. Chem., Vol. 263, Issue 16, 7655-7659, Jun, 1988
The NH2-terminal 21 amino acid residues are not essential for the papain-inhibitory activity of oryzacystatin, a member of the cystatin superfamily. Expression of oryzacystatin cDNA and its truncated fragments in Escherichia coli
K Abe, Y Emori, H Kondo, S Arai and K Suzuki
Department of Agricultural Chemistry, University of Tokyo, Japan.
Oryzacystatin, a proteinaceous cysteine proteinase inhibitor (cystatin) in
rice, is comprised of 102 residues (Met1-Ala102) (Abe, K., Emori, Y.,
Kondo, H., Suzuki, K., and Arai, S. (1987) J. Biol. Chem. 262,
16793-16797). We constructed an expression plasmid containing a full length
oryzacystatin cDNA at the multi-cloning site of pUC18 and produced a
lacZ'-oryzacystatin fusion protein in Escherichia coli. The partially
purified expressed protein efficiently inhibits papain activity assayed
using N-benzoyl-DL-arginine-2-naphthylamide as a substrate. We also
constructed expression plasmids lacking the 5'- and 3'-regions of cDNAs
that encode NH2- and COOH-terminally truncated oryzacystatins. An
N-truncated oryzacystatin lacking Gly5 and retaining
Gln53-Val54-Val55-Ala56-Gly57 inhibited papain as efficiently as the full
length oryzacystatin, although both Gly5 and Gln53-Gly57 (oryzacystatin
numbering) are conserved among members of most cystatin superfamilies.
However, another N-truncated oryzacystatin lacking the NH2-terminal 38
residues was almost completely inactive. On the other hand, a
COOH-terminally truncated oryzacystatin lacking the COOH- terminal 11
residues possesses potent papain-inhibitory activity, whereas another
COOH-terminally truncated oryzacystatin lacking 35 residues shows much less
inhibitory activity, although it retains the two well conserved features
Gly5 and Gln53-Gly57. These results indicate that the NH2-terminal 21
residues containing Gly5 and the COOH- terminal 11 residues are not
essential, suggesting that a portion of the polypeptide segment containing
Gln53-Gly57 is necessary for oryzacystatin to elicite its papain-inhibitory
activity efficiently.