Conformation
nearby Trp Residues of APIA and APIB Modulates the Inhibitory Specificity of
the Protease
LI Jiong, CHI Cheng-Wu, RUAN Kang-Cheng*
( Institute of Biochemistry and Cell Biology, Shanghai Institutes for
Biological Sciences, the Chinese Academy of Science, Shanghai 200031,
China )
Abstract The
relationship between the micro-environment of the two tryptophan residues and
the inhibitory specificity of arrowhead protease inhibitors A and B (APIA and
APIB) was studied by mutagenesis and fluorescence spectroscopy. The environment
of the two Trp residues at positions 93 and 122 in APIB is more hydrophobic
than in APIA. Study after substitution of Trp with Ala revealed that the
environment of Trp122 is more hydrophobic than that of Trp93. Substitution of Leu82 and
Arg87 in APIB with Ser and Leu respectively made the tryptophan
fluorescence of APIB to be like that of APIA and the inhibitory specificity to be closer to APIA,
indicating that the inhibitory specificity of the enzyme may be modulated by the conformation around
the tryptophan residues.
Key words arrowhead protease inhibitors£» site-directed mutagenesis£» fluorescence emission spectra£» conformation£» inhibitory specificity
*Corresponding author£ºTel, 86-21-64740532; Fax,
86-21-64338357£» e-mail, [email protected]