Sequestration of the active site by interdomain shifting: crystallographic and spectroscopic evidence for distinct conformations of L-3-Hydroxyacyl-CoA dehydrogenase

Dimeric Crystal Structure of Rabbit l-Gulonate 3-Dehydrogenase/λ-Crystallin: Insights into the Catalytic Mechanism

“…This is probably due to a difference in recognition residues for the carboxyamide moiety of nicotinamide: three residues Leu16, Ser20, and Asn148 in GDH, and only Asn161 in HAD. 9,11 In addition, the interaction of Gln41 with the hydroxyl groups of the adenine ribose in the GDH structure differs from that of the corresponding residue (Gln46) of HAD. The coenzyme-binding residues of GDH outnumber those of HAD.…”

“…7b) using structural information from the active-site residues and the C-4 atom of nicotinamide moiety as guide. In particular, the positions of residues His145 and Arg231 were useful in orienting the 3-hydroxyl group and the carboxyl group, respectively, of L-gulonate molecule, since the equivalent histidine residue in the human HAD (His157) has been assigned as the catalytic base involved in hydride transfer 11 and since Arg231 is suggested in this study as a key residue that binds the carboxylate moiety of gulonate. The modeled substrate molecule resides in the positively charged active-site pocket of the rabbit GDH dimer.…”

“…9 Furthermore, the coenzyme-induced conformational change in Ser124 found in this study was not observed in the studies of human HAD. 9,11,12 In our comparison of the human HAD crystal structures, including the apoenzyme form (PDB accession code 1F14), NADH-bound form (PDB accession code 1F17), and NAD + -bound form (PDB accession code 3HAD), the side chain of Ser137, corresponding to the Ser124 of GDH, shows only one conformation, which is not similar to the two conformers seen in the GDH/NADH complex. By contrast, the orientation of the Ser137 side chain in the human HAD/NAD + /acetoacetylCoA ternary complex (PDB accession code 1F0Y) is almost identical with that of the conformer-2 Ser124 of GDH, further supporting that conformer-2 is the catalytically active state of Ser124.…”

Crystal structure of 5-formyl-3-hydroxy-2-methylpyridine 4-carboxylic acid 5-dehydrogenase, an NAD+-dependent dismutase from Mesorhizobium loti

“…A conserved His-Glu dyad is vital for HAD catalytic mechanism. The His residue acts as a catalytic/general base [11][12][13][14][15][16]. In HhHAD, His158 has been proposed as the catalytic base and Glu170 is involved in proper orientation of the His residue.…”

“…HADs have been found in mitochondria and peroxisomes of different species [7][8][9]. The crystal structures of HAD from pig [10], Caenorhabditis elegans [11] and human [12] have been solved and the catalytic mechanism of human heart HAD has been proposed [13]. FHMPCDH shares 32% identity with human heart 3-hydroxyacyl-CoA dehydrogenase (HhHAD).…”