Search

Research reveals that chimeras of the alpha(sub)1-antitrypsin efficiently inhibit papain-like cysteine protease and that the inhibition is a function of the length of the reactive center loop. Data indicate that the inhibition requires insertion of the reactive center loop into the body of the cysteine protease body.

Amino acid substitution studies reveal that the F-helix of the serpin alpha(sub)1-antitrypsin Abeta-sheet is highly disrupted in conformation, suggesting that the F-helix plays a role in the early conformational changes of the protein unfolding. The substitution of Tyr160 to alanine leads to loss of hydrogen bond and protein stability but restored by tryptophan.

The mouse SQN-5 serpin inhibits both chymotrypsin-like serine and the papain-like cysteine proteinases through a reactive site loop-dependent inhibitory mechanism. Data indicate that the human and mouse serpin genes seem to have originated from a common ancestor.

Research has been conducted on the members of the serpine family human squamous cell carcinoma antigens (SCCA) 1 and 2. The SCCA1 inhibition mechanism is described.

The hydrolysis of substrates representing cleavage sequences in the physiological substrates for Clr and Cls is examined. The importance of prime subsites in Cls for interaction with its cognate substrates in the complement pathway yielding greater understanding of the mechanism of interaction between the vital protease and its physiological substrates is highlighted.

A study conducted to map the preference of the gingipain-R enzymes for prime site amino acid residues in peptide substrates is presented. It was found that the gingipains were relatively nonspecific for these residues and that no marked difference in specificity could be found between different forms of the gingpains-R.

Results indicate that the Phe77 to Leu mutation in the shutter region of the serine proteinase inhibitor, antithrombin, results in conformational changes around the D-helix top of the inhibitor involving arginine 132 and 133 residues, which mediate antithrombin/heparin interactions.

Research has been conducted on serpin superfamily member hurpin, linked to human keratinocyte apoptosis. Results deminstrate that hurpin is an inhibitor of the archetypal lysosome cysteine proteinase cathepsin L.

The shutter region of serpins consists of a number of highly conserved residues that are critical for both stability and function. Several variants of antithrombin with substitutions in this region are unstable and predispose the carrier to thrombosis. Although most mutations in the shutter region investigated to date are deleterious with respect to serpin stability and function, the substitution of Phe51 by Leu in alpha(1)-antitrypsin results in enhanced stability. Here, we have investigated the effects of introducing an analogous mutation into antithrombin (Phe 77 to Leu). The mutation did not affect the kinetics of interaction with proteases. Strikingly, however, the thermostability of the protein was markedly decreased, with the serpin displaying a 13 degrees C decrease in melting temperature as compared to wild-type recombinant antithrombin. Further studies revealed that in contrast to wild-type antithrombin, the mutant adopted the latent (inactive) conformation upon mild heating. Previous studies on shutter region mutations that destabilize antithrombin revealed that such variants possess enhanced affinity for both heparin pentasaccharide and full-length heparin. The N135A/F77L mutant had unchanged affinity for heparin pentasaccharide, but the affinity for full-length heparin was increased. We suggest that the Phe77Leu mutation causes conformational changes around the top of the D-helix in antithrombin, in particular, to the arginine 132 and 133 residues that may mediate additional antithrombin/heparin interactions. This paper also demonstrates that there are major differences between the shutter regions of antithrombin and alpha(1)-antitrypsin since a stabilizing mutation in antitrypsin has the converse effect in antithrombin.