Publication Date:
2013-10-29
Description:
Oligopeptidase B (OPB) is a member of the prolyl oligopeptidase (POP) family of serine proteases. OPB in trypanosomes is an important virulence factor and potential pharmaceutical target. Characteristic structural features of POP family members include lack of a propeptide and presence of a β-propeller domain (PD), although the role of the β-PD has yet to be fully understood. In this work, residues Glu 172 , Glu 490 , Glu 524 and Arg 689 in Trypanosoma brucei OPB (Tb OPB), which are predicted to form inter-domain salt bridges, were substituted for Gln and Ala, respectively. These mutants were evaluated in terms of catalytic properties and stability. A negative effect on kcat/Km was obtained following mutation of Glu 172 or Arg 689 . In contrast, the E490Q mutant exhibited markedly decreased thermal stability, although this mutation had less effect on catalytic properties compared to the E172Q and R689A mutants. Trypsin digestion showed that the boundary regions between the β-PD and catalytic domains (CDs) of the E490Q mutant are unfolded with heat treatment. These results indicated that Glu 490 in the CD plays a role in stabilization of Tb OPB, whereas Glu 172 in the β-PD is critical for the catalytic activity of Tb OPB.
Print ISSN:
0021-924X
Electronic ISSN:
1756-2651
Topics:
Biology
,
Chemistry and Pharmacology
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