This old version of Proteopedia is provided for student assignments while the new version is undergoing repairs. Content and edits done in this old version of Proteopedia after March 1, 2026 will eventually be lost when it is retired in about June of 2026.
Apply for new accounts at the new Proteopedia. Your logins will work in both the old and new versions.
2d38
From Proteopedia
The Crystal Structure of Flavin Reductase HpaC complexed with NADP+
Overview
4-Hydroxyphenylacetate (4-HPA) is oxidized as an energy source by two component enzymes, the large component (HpaB) and the small component (HpaC). HpaB is a 4-HPA monooxygenase that utilizes FADH(2) supplied by a flavin reductase HpaC. We determined the crystal structure of HpaC (ST0723) from the aerobic thermoacidophilic crenarchaeon Sulfolobus tokodaii strain 7 in its three states [NAD(P)(+)-free, NAD(+)-bound, and NADP(+)-bound]. HpaC exists as a homodimer, and each monomer was found to contain an FMN. HpaC preferred FMN to FAD because there was not enough space to accommodate the AMP moiety of FAD in its flavin-binding site. The most striking difference between the NAD(P)(+)-free and the NAD(+)/NADP(+)-bound structures was observed in the N-terminal helix. The N-terminal helices in the NAD(+)/NADP(+)-bound structures rotated ca. 20 degrees relative to the NAD(P)(+)-free structure. The bound NAD(+) has a compact folded conformation with nearly parallel stacking rings of nicotinamide and adenine. The nicotinamide of NAD(+) stacked the isoalloxazine ring of FMN so that NADH could directly transfer hydride. The bound NADP(+) also had a compact conformation but was bound in a reverse direction, which was not suitable for hydride transfer.
About this Structure
2D38 is a Single protein structure of sequence from Sulfolobus tokodaii str. 7. Full crystallographic information is available from OCA.
Reference
Crystal structures of the short-chain flavin reductase HpaC from Sulfolobus tokodaii strain 7 in its three states: NAD(P)(+)(-)free, NAD(+)(-)bound, and NADP(+)(-)bound., Okai M, Kudo N, Lee WC, Kamo M, Nagata K, Tanokura M, Biochemistry. 2006 Apr 25;45(16):5103-10. PMID:16618099 Page seeded by OCA on Sat May 3 23:37:00 2008
