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GTP cyclohydrolase II structure and mechanism
Jingshan Ren1, Masayo Kotaka, Michael Lockyer
1Division of Structural Biology, The Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford, OX3 7BN, United Kingdom.
The Journal of Biological Chemistry
|August 24, 2005
Summary
GTP cyclohydrolase II is crucial for riboflavin biosynthesis and a potential antimicrobial target. Its distinct structure and mechanism from GTP cyclohydrolase I, revealed by X-ray crystallography, offer new avenues for drug development.
Area of Science:
- Biochemistry
- Structural Biology
- Drug Discovery
Background:
- Guanosine triphosphate (GTP) cyclohydrolase II (GCH2) is essential for riboflavin biosynthesis.
- Riboflavin is vital for metabolism, and GCH2's absence in higher eukaryotes presents a selective antimicrobial drug target.
- GCH2 differs significantly from GTP cyclohydrolase I (GCHI), which is involved in folate and tetrahydrobiopterin biosynthesis.
Purpose of the Study:
- To elucidate the structural basis of GTP recognition and catalysis by GCH2.
- To compare the structural and mechanistic differences between GCH2 and GCHI.
- To provide insights for the development of novel antimicrobial agents targeting GCH2.
Main Methods:
- X-ray crystallography of GTP cyclohydrolase II (GCH2) at 1.54-Å resolution.
- Determination of the GCH2.GMPCPP complex structure.
- Comparative analysis of GCH2 and GCHI structures and catalytic mechanisms.
Main Results:
- GCH2 possesses a distinct protein fold and unique GTP recognition determinants compared to GCHI.
- Structural analysis revealed key residues, Arg(128) and Tyr(105), involved in GTP binding, pyrophosphate release, and ring opening.
- Both GCH2 and GCHI utilize a catalytic zinc ion but employ different residues for GTP ring opening and formate release.
Conclusions:
- The determined structure of GCH2 provides a detailed mechanistic understanding of its role in riboflavin biosynthesis.
- Structural differences between GCH2 and GCHI highlight GCH2 as a promising selective target for antimicrobial drug development.
- The findings facilitate structure-based drug design strategies targeting essential bacterial pathways.