THE EFFECTS OF REACTIVE CENTER LOOP LENGTH UPON SERPIN POLYMERIZATION

The clinical effects of serpin polymerisation include thromboembolism, emphysema, and liver disease. A thorough understanding of serpin poly merisation mechanisms and the structures involved will permit the rati onal design of therapeutic polymerisation inhibitors. Here we show tha t serpin polymerisation can be delayed by extending the length of the serpin reactive centre loop. The heat stability of three chimeric serp ins was examined. One of them, an active alpha(1)-antitrypsin variant with a reactive centre loop C-terminal extension of four amino acid re sidues, was shown to have increased resistance to inactivation by poly merisation. This variant could also form serpin/peptide binary complex es with a reactive centre loop peptide, which indicates that the incre ase in thermostability was not due to the A-beta-sheet being unable to accept reactive centre loop residues, an essential requirement for po lymerisation. Rather we conclude that the additional residues within t he reactive centre loop delay the release of strand 1C from the C-shee t, a process essential for polymer formation. (C) 1997 Academic Press.