Crystal structure of the parasite inhibitor chagasin in complex with papain allows identification of structural requirements for broad reactivity and specificity determinants for target proteases Izabela Redzynia1,*, Anna Ljunggren2,*, Anna Bujacz1, Magnus Abrahamson2, Mariusz Jaskolski3,4 and Grzegorz Bujacz1,4 1 Institute of Technical Biochemistry, Faculty of Biotechnology and Food Sciences, Technical University of Lodz, Poland 2 Department of Laboratory Medicine, Division of Clinical Chemistry and Pharmacology, Lund University, Sweden 3 Department of Crystallography, Faculty of Chemistry, A. Mickiewicz University, Poznan, Poland 4 Center for Biocrystallographic Research, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland Keywords A complex of chagasin, a protein inhibitor from Trypanosoma cruzi, and Chagas disease; cruzipain; cysteine papain, a classic family C1 cysteine protease, has been crystallized. Kinetic proteases; papain; protein inhibitors studies revealed that inactivation of papain by chagasin is very fast ) ) (k = 1.5 · 106 m 1Æs 1), and results in the formation of a very tight, Correspondence on m G. Bujacz, Institute of Technical Biochemis- reversible complex (Ki =36p ), with similar or better rate and equilib- try, Faculty of Biotechnology and Food rium constants than those for cathepsins L and B. The high-resolution Sciences, Technical University of Lodz, ul. crystal structure shows an inhibitory wedge comprising three loops, which Stefanowskiego 4/10, 90-924 Lodz, Poland forms a number of contacts responsible for the high-affinity binding. Com- Fax: +48 42 636 66 18 parison with the structure of papain in complex with human cystatin B Tel: +48 42 631 34 31 reveals that, despite entirely different folding, the two inhibitors utilize very E-mail:
[email protected] similar atomic interactions, leading to essentially identical affinities for the M.