Structure and Mechanistic Implications of a Uroporphyrinogen III Synthase−Product Complex
Uroporphyrinogen III synthase (U3S) catalyzes the asymmetrical cyclization of a linear tetrapyrrole to form the physiologically relevant uroporphyrinogen III (uro'gen III) isomer during heme biosynthesis. Here, we report four apoenzyme and one product complex crystal structures of the Thermus thermophilus (HB27) U3S protein. The overlay of eight crystallographically unique U3S molecules reveals a huge range of conformational flexibility, including a 'closed' product complex. The product, uro'gen III, binds between the two domains and is held in place by a network of hydrogen bonds between the product's side chain carboxylates and the protein's main chain amides. Interactions of the product A and B ring carboxylate side chains with both structural domains of U3S appear to dictate the relative orientation of the domains in the closed enzyme conformation and likely remain intact during catalysis. The product C and D rings are less constrained in the structure, consistent with the conformational changes required for the catalytic cyclization with inversion of D ring orientation. A conserved tyrosine residue is potentially positioned to facilitate loss of a hydroxyl from the substrate to initiate the catalytic reaction.
- Research Organization:
- Brookhaven National Laboratory (BNL) National Synchrotron Light Source
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- AC02-98CH10886
- OSTI ID:
- 959826
- Report Number(s):
- BNL--82812-2009-JA
- Journal Information:
- Biochemistry, Journal Name: Biochemistry Journal Issue: 33 Vol. 47; ISSN 0006-2960; ISSN BICHAW
- Country of Publication:
- United States
- Language:
- English
Similar Records
Spectroscopic evidence for a porphobilinogen deaminase-tetrapyrrole complex that is an intermediate in the biosynthesis of uroporphyrinogen III
Substrate Shuttling Between Active Sites of Uroporphyrinogen Decarboxylase in Not Required to Generate Coproporphyrinogen
Human uroporphyrinogen III synthase: Molecular cloning, nucleotide sequence, and expression of a full-length cDNA
Journal Article
·
Tue Jun 28 00:00:00 EDT 1988
· Biochemistry; (United States)
·
OSTI ID:6864067
Substrate Shuttling Between Active Sites of Uroporphyrinogen Decarboxylase in Not Required to Generate Coproporphyrinogen
Journal Article
·
Wed Dec 31 23:00:00 EST 2008
· Journal of Molecular Biology
·
OSTI ID:980579
Human uroporphyrinogen III synthase: Molecular cloning, nucleotide sequence, and expression of a full-length cDNA
Journal Article
·
Sat Oct 01 00:00:00 EDT 1988
· Proceedings of the National Academy of Sciences of the United States of America; (USA)
·
OSTI ID:5478379