2G18

Crystal Structure of Nostoc sp. 7120 phycocyanobilin:ferredoxin oxidoreductase (PcyA) Apoprotein

Summary for 2G18

• Entry DOI: 10.2210/pdb2g18/pdb
• Descriptor: Phycocyanobilin:ferredoxin oxidoreductase, CALCIUM ION (3 entities in total)
• Functional Keywords: alpha-beta-alpha sandwich, oxidoreductase
• Biological source: Anabaena sp.
• Total number of polymer chains: 12
• Total formula weight: 345107.65

Authors

Tu, S.-L.,Lagarias, J.C.,Fisher, A.J. (deposition date: 2006-02-13, release date: 2006-12-26, Last modification date: 2024-02-14)

Primary citation

Tu, S.L.,Rockwell, N.C.,Lagarias, J.C.,Fisher, A.J.
Insight into the radical mechanism of phycocyanobilin-ferredoxin oxidoreductase (PcyA) revealed by X-ray crystallography and biochemical measurements.
Biochemistry, 46:1484-1494, 2007

PubMed Abstract: The X-ray crystal structure of the substrate-free form of phycocyanobilin (PCB)-ferredoxin oxidoreductase (PcyA; EC 1.3.7.5) from the cyanobacterium Nostoc sp. PCC7120 has been solved at 2.5 A resolution. A comparative analysis of this structure with those recently reported for substrate-bound and substrate-free forms of PcyA from the cyanobacterium Synechocystis sp. PCC6803 (Hagiwara et al. (2006) Proc. Natl. Acad. Sci. U.S.A. 103, 27-32; Hagiwara et al. (2006) FEBS Lett. 580, 3823-3828) provides a compelling picture of substrate-induced changes in the PcyA enzyme and the chemical basis of PcyA's catalytic activity. On the basis of these structures and the biochemical analysis of site-directed mutants of Nostoc PcyA, including mutants reported in recent studies (Tu et al. (2006) J. Biol. Chem. 281, 3127-3136) as well as mutants described in this study, a revised mechanism for the PcyA-mediated four-electron reduction of biliverdin IXalpha to 3E/3Z-phycocyanobilin via enzyme-bound bilin radical intermediates is proposed. The mechanistic insight of these studies, along with homology modeling, have provided new insight into the catalytic mechanisms of other members of the ferredoxin-dependent bilin reductase family that are widespread in oxygenic photosynthetic organisms.

PubMed: 17279614
DOI: 10.1021/bi062038f

Experimental method

X-RAY DIFFRACTION (2.5 Å)