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Re: [ccp4bb]: isomerization of non-proline cis/trans peptide bond

We have observed this behaviour, but in the context of two distinct crystal
structures. An active site Leu-Lys peptide bond in Toxoplasma gondii HGPRT can
be cis or trans (structures at 1.8 and 1.6 A resolution). We proposed that such
isomerization is an integral part of the enzymatic reaction mechanism. The
references are:

Annie Héroux, E. Lucile White, Larry J. Ross and David W. Borhani. "Crystal
Structure of Toxo-plasma gondii Hypoxanthine-Guanine Phosphoribosyltransferase
with XMP, Pyrophosphate, and Two Mg2+ Ions Bound: Insights into the Catalytic
Mechanism." Biochemistry 1999, 38, 14495-14506.

Annie Héroux, E. Lucile White, Larry J. Ross and David W. Borhani. "Crystal
Structures of the Toxoplasma gondii Hypoxanthine-Guanine
Phosphoribosyltransferase-GMP and -IMP Complexes: Comparison of Purine Binding
Interactions with the XMP Complex." Biochemistry 1999, 38, 14485-14494.

David Borhani
Abbott Bioresearch Center, Inc.

Rong-Jin Guan <ziweiguan@yahoo.com> on 06/10/2001 04:51:54 AM
To:   ccp4bb
Subject:  [ccp4bb]: isomerization of non-proline cis/trans peptide bond

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Dear Crystallographers,
I have found an intersting feature in my structure:
there are 2 molecules in the asym. unit, and the first
one contains a definite non-proline peptide bond,
at the same position in the second molecule it seems
the cis peptide bond isomerizes between cis and trans
conformation. I do not know what cuases the

has anybody the similar experiences? I would like to
hear your valuable comments.

Rong-jin Guan

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