X-Ray Structure Determination at 2.6-Å Resolution of a Lipoate-Containing Protein: The H-Protein of the Glycine Decarboxylase Complex From Pea Leaves

• Published in: Proceedings of the National Academy of Sciences - PNAS 1994-05, Vol.91 (11), p.4850-4853
• Main Authors: Pares, Serge, Cohen-Addad, Claudine, Sieker, Larry, Neuburger, Michel, Douce, Roland
• Format: Article
• Language: English
• Subjects: Amino Acid Oxidoreductases - chemistry; Amino Acid Sequence; Animals; Atoms; Biochemistry; Carrier Proteins - chemistry; Crystal structure; Crystallography, X-Ray; Crystals; Enzymes; Fabaceae - chemistry; Flowers & plants; Glycine Decarboxylase Complex; Glycine Decarboxylase Complex H-Protein; Glycine Dehydrogenase (Decarboxylating); Humans; Mitochondria; Molecular Sequence Data; Molecules; Peas; Plants, Medicinal; Protein Conformation; Proteins; Sandwich structures; Sequence Homology, Amino Acid; Thioctic Acid - chemistry; Ungulates
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.91.11.4850

H-protein, a lipoic acid-containing protein of the glycine decarboxylase (EC 1.4.4.2) complex from pea (Pisum sativum) was crystallized from ammonium sulfate solution at pH 5.2 in space group P3121. The x-ray crystal structure was determined to 2.6-Å resolution by multiple isomorphous replacement techniques. The structure was refined to an R value of 23% for reflections between 15- and 2.6-overset⚬ A resolution (F > 2σ), including the lipoate moiety and 50 water molecules, for the two protein molecules of the asymmetric unit. The 131-amino acid residues form seven β-strands arranged into two antiparallel β-sheets forming a "sandwich" structure. One α-helix is observed at the C-terminal end. The lipoate cofactor attached to Lys-63 is located in the loop of a hairpin configuration. The lipoate moiety points toward the residues His-34 and Asp-128 and is situated at the surface of the H-protein. This allows the flexibility of the lipoate arm. This is the first x-ray determination of a lipoic acid-containing protein, and the present results are in agreement with previous theoretical predictions and NMR studies of the catalytic domains of lipoic acid- and biotin-containing proteins.