MUTEINS OF BETA-GALACTOSIDASE FRAGMENTS HAVING INCREASED ACTIVITY

摘要

Muteins of enzyme acceptor polypeptide fragments of beta -galactosidase are provided which exhibit substantially increased kinetic complementation activity with no significant loss in stability. A preferred enzyme acceptor fragment has an amino acid other than cysteine located at position 500 of the natural sequence. An especially preferred substitution is serine or valine. Other preferred muteins have an amino acid other than methionine located at position 443, with leucine being especially preferred, or an amino acid other than cysteine at position 76, with leucine being an especially preferred substitution. Also provided are methods for producing the novel muteins, reagent compositions comprising the novel muteins, and immunoassay methods for determining an analyte in which the novel mutein recombines with an enxyme donor polypeptide fragment to form enzymatically active beta -galactosidase.