A large number of point mutations
have been performed on squash trypsin inhibitors
The trypsin selectivity of EETI-II was changed to elastase
and α-chymotrypsin by modification of the P1 residue [Favel et al., 1989;
Le-Nguyen et al.,
1990]. Similar results were obtained for another squash inhibitor,
et al., 1989].
Numerous mutants of CMTI-I and CMTI-III were reported, mainly
by polish groups.
CMTI-III mutants of the Arg5 P1 residue exhibit antitrypsin,
antichymotrypsin or antielastase activity [Rolka
et al., 1989; Rolka
et al., 1991, Rozycki
Double mutants with Tyr27-Val mutation and Glycine in position
9, 11, 14, 17, 19 or 29 reduce association equilibrium constants
by 6-7 orders of magnitude [Rozycki
et al., 1993].
Several mutations outside the contact region did not change the
antitrypsin activity [Rozycki
et al., 1994b].
while other mutations outside the binding loop did affect binding
to trypsin [Jaskiewicz
et al., 1998].
Mutants of CMTI-I were recently screened for inhibition of serine
protease from human blood clotting system [Grzesiak
et al., 2000].
Mutation one to four of four conserved hydrophobic residues in
CMTI-I were replaced by alanine. Single replacements led to 5-40
times less effective trypsin inhibitors whereas the quadruple
mutant was approximately 450 times less effective [Kojima
et al., 1996].
The conservative Met8-Leu mutation in CMTI-I was shown to affect
both stability and folding of the protein [Zhukov
et al., 2000].
The impact of mutation Trp7Leu and addition of Asn25 in MCTI-II,
on inhibition of factor Xa and on factor X activation, has been
studied [Kamei et
The Potato Carboxypeptidase Inhibitor
Residues of the C-terminal tail were
screened by directed mutagenesis for their role in the interaction
with carboxypeptidase [Marino-Buslje
et al., 2000; Molina
et al., 1994].
The cyclotide kalata B1 is tolerant to point mutations
Structural studies of [W19K/P20N/V21K] kalata B1 and [P20D/V21K] kalata B1
showed that the cyclotide framework is tolerant to residue substitutions
[Clark et al., 2006].