African Journal of Biochemistry Research
www.academicjournals.org/ajbr
Dear Collegue,
We received a manuscript titled: **
The contribution of Ser463 residue to the enzymatic and autoprocessing
activities of *Escherichia coli *=83=D7-glutamyltranspeptidase
Below you will find the abstract
A serine residue, Ser463, required for the proper function of *Escherichia
coli* g-glutamyltranspeptidase (*Ec*GGT) was identified by site-directed
mutagenesis on the basis of sequence alignment of human, pig, rat, and thre=
e
bacterial enzymes. Thr-, Asp-, and Lys-substituted variants were
overexpressed in *E. coli *M15 cells and the recombinant proteins were
purified to near homogeneity by nickel-chelate chromatography. With the
exception of S463T, the other two variants completely lost GGT activity,
implying the importance of this residue in *Ec*GGT. Moreover, substitution
of Ser463 with either Lys or Asp impaired the capability of autocatalytic
processing of the precursor into a- and b-subunit. Computer modeling showed
that the critical bonding distance of Gln390 C-Thr391 OG1 is significantly
increased in S463D and S463K, indicating that these distance changes might
be responsible for the lack of enzyme maturation. Measurements of intrinsic
tryptophan fluorescence revealed alteration of the microenvironment of
aromatic amino acid residues in S463D and S463K, while circular dichroism
spectra were nearly identical for wild-type and all mutant enzymes. The
temperature-dependent signal in the far-UV region for S463T was consistent
with that of wild-type enzyme but S463D and S463K showed a different
sensitivity towards temperature-induced denaturation. These results imply
that a significant conformational change occurred as a result of Asp- and
Lys-substitution.
Key words: *Escherichia coli*, g-glutamyltranspeptidase, site-specific
mutagenesis, autocatalytic processing, tryptophan emission fluorescence,
circular dichroism
i am looking forward to your response if you are interested in reviewing.
Best regards,
Prof. Johnson Lin
Editor, African Journal of Biochemistry Research
E-mail: * **ajbr.acadjourn from gmail.com* <ajbr from academicjournals.org>
http://www.academicjournals.org/AJBR
