Photoaffinity labeling of D-(-)-beta-hydroxybutyrate dehydrogenase by (arylazido)-beta-alanyl-substituted nicotinamide adenine dinucleotide

Alkylation at the active site of the D-3-hydroxybutyrate dehydrogenase (BDH), a membrane phospholipid-dependent enzyme, by 3-chloroacetyl pyridine adenine dinucleotide (3-CAPAD)

The structure of the rat liver's D-3-hydroxybutyrate dehydrogenase (BDH) active site has been investigated using an affinity alkylating reagent, the 3-chloroacetyl pyridine adenine dinucleotide (3-CAPAD). This NAD+ analogue reagent strongly inactivates the enzyme following a concentration- and time-dependent process with a stoichiometry of approximately 1. The reagent reacts at the coenzyme binding site as revealed by the efficient protection by NADH. The effect of 3-CAPAD is stronger with the enzyme into its natural membrane environment than with the lipid-free purified apoBDH or with the reconstituted apoBDH-mitochondrial phospholipid complex. The pH-dependent effect on the inactivation process is in agreement with the participation of protons in the catalytic mechanism of BDH. Furthermore, this study exhibits the phospholipid activating role in BDH catalytic activation.

N-arylazido-beta-alanyl-NAD+, a new NAD+ photoaffinity analogue. Synthesis and labeling of mitochondrial NADH dehydrogenase

N-Arylazido-beta-alanyl-NAD+ [N3'-O-(3-[N-(4-azido-2-nitrophenyl)amino]propionyl)NAD+] has been prepared by alkaline phosphatase treatment of arylazido-beta-alanyl-NADP+ [N3'-O-(3-[N-(4-azido-2-nitrophenyl)amino]propionyl)NADP+]. This NAD+ analogue was found to be a potent competitive inhibitor (Ki = 1.45 microM) with respect to NADH for the purified bovine heart mitochondrial NADH dehydrogenase (EC 1.6.99.3). The enzyme was irreversibly inhibited as well as covalently labeled by this analogue upon photoirradiation. A stoichiometry of 1.15 mol of N-arylazido-beta-alanyl-NAD+ bound/mol of enzyme, at 100% inactivation, was determined from incorporation studies using tritium-labeled analogue. Among the three subunits, 0.85 mol of the analogue was bound to the Mr = 51,000 subunit, and each of the two smaller subunits contained 0.15 mol of the analogue when the dehydrogenase was completely inhibited upon photolysis. Both the irreversible inactivation and the covalent incorporation could be prevented by the presence of NADH during photolysis. These results indicate that N-arylazido-beta-alanyl-NAD+ is an active-site-directed photoaffinity label for the mitochondrial NADH dehydrogenase, and are further evidence that the Mr = 51,000 subunit contains the NADH binding site. Previous studies using A-arylazido-beta-alanyl-NAD+ [A3'-O-(3-[N-(4-azido-2-nitrophenyl)amino]propionyl)NAD+] demonstrated that the NADH binding site is on the Mr = 51,000 subunit [Chen, S., & Guillory, R. J. (1981) J. Biol. Chem. 256, 8318-8323]. Results are also presented to show that N-arylazido-beta-alanyl-NAD+ binds the dehydrogenase in a more effective manner than A-arylazido-beta-alanyl-NAD+.

Amino acid sequence of the nucleotide-binding site of D-(-)-beta-hydroxybutyrate dehydrogenase labeled with arylazido-beta-[3-3H]alanylnicotinamide adenine dinucleotide

In the dark, arylazido-beta-alanylnicotinamide adenine dinucleotide (N3-NAD) can replace NAD as cofactor for D-(-)-beta-hydroxybutyrate dehydrogenase (BDH) purified from bovine heart mitochondria. When photoirradiated with visible light, N3-NAD forms a nitrene species that binds covalently to BDH and inhibits the enzyme. NAD(H) protects BDH against photolabeling and inhibition by N3-NAD [Yamaguchi, M., Chen, S., & Hatefi, Y. (1985) Biochemistry 24, 4912-4916]. In the present study, a tryptic peptide of purified BDH photolabeled with arylazido-beta-[3-3H] alanyl-NAD [( 3H]N3-NAD) was isolated and sequenced. The same tryptic peptide was also isolated from BDH not labeled with [3H]N3-NAD and sequenced. Both peptides indicated the sequence Met-Glu-Ser-Tyr-Cys-Thr-Ser-Gly-Ser-Thr-Asp-Thr-Ser-Pro-Val-Ile-Lys. The residue labeled with [3H]N3-NAD was Cys. This heptadecapeptide contains 14 uncharged residues and is marked by having in an undecapeptide segment 8 hydroxy amino acids located symmetrically around a central glycine.

Inactivation of D-(-)-beta-hydroxybutyrate dehydrogenase by modifiers of carboxyl and histidyl groups

Data presented in this paper suggest that D-(-)-beta-hydroxybutyrate dehydrogenase (BDH) purified from bovine heart mitochondria contains an essential carboxyl group and an essential histidyl residue at or near the active site. Lactate and malate dehydrogenases, which catalyze reactions analogous to that catalyzed by BDH, also contain an aspartyl and a histidyl residue at the active site [Birktoft, J.J., & Banaszak, L.J. (1983) J. Biol. Chem. 258, 472-482]. In addition, all three enzymes contain an essential arginyl residue, apparently concerned with electrostatic interaction with their respective carboxylic acid substrates, and promote ternary adduct formation involving the enzyme, NAD, and sulfite.

Lipid-protein interactions in biomembranes studied through the phospholipid specificity of D-beta-hydroxybutyrate dehydrogenase

Since the biological membranes are fundamental units in the living cells, the studies of lipid-protein interactions are crucial for the understanding of their structure, functions and properties. Beside hydrophobic interactions between fatty acids chain of phospholipids and intrinsic membrane proteins, the interactions between charged groups of the protein with the polar heads of phospholipids generally confer the specificity which may be absolute or preferential. This paper reports essential results obtained these last few years with D-beta-hydroxybutyrate dehydrogenase (BDH) from inner mitochondrial membrane, one of the most interesting and best documented examples of a lipid-requiring enzyme. This is a review of the molecular basis--knowledge and strategy of study--of the lipid specificity for membrane protein functions.