Structural Framework for Metal Incorporation during Molybdenum Cofactor Biosynthesis

• Published in: Structure (London) 2016-05, Vol.24 (5), p.782-788
• Main Authors: Kasaragod, Vikram Babu, Schindelin, Hermann
• Format: Article
• Language: English
• Subjects: Adenosine Diphosphate - metabolism; Adenosine Monophosphate - metabolism; Binding Sites; Carrier Proteins - chemistry; Carrier Proteins - genetics; Carrier Proteins - metabolism; Coenzymes - biosynthesis; Coenzymes - chemistry; Humans; Membrane Proteins - chemistry; Membrane Proteins - genetics; Membrane Proteins - metabolism; Metalloproteins - biosynthesis; Metalloproteins - chemistry; Molybdenum - metabolism; Mutation; Protein Binding; Pteridines - chemistry
• ISSN: 0969-2126; 1878-4186
• DOI: 10.1016/j.str.2016.02.023

The molybdenum cofactor (Moco) is essential for the catalytic activity of all molybdenum-containing enzymes with the exception of nitrogenase. Moco biosynthesis follows an evolutionarily highly conserved pathway and genetic deficiencies in the corresponding human enzymes result in Moco deficiency, which manifests itself in severe neurological symptoms and death in childhood. In humans the final steps of Moco biosynthesis are catalyzed by gephyrin, specifically the penultimate adenylation of molybdopterin (MPT) by its N-terminal G domain (GephG) and the final metal incorporation by its C-terminal E domain (GephE). To better understand the poorly defined molecular framework of this final step, we determined high-resolution crystal structures of GephE in the apo state and in complex with ADP, AMP, and molybdate. Our data provide novel insights into the catalytic steps leading to final Moco maturation, namely deadenylation as well as molybdate binding and insertion. [Display omitted] •Structural basis for the terminal step of molybdenum cofactor biosynthesis•ADP/AMP bind to the Rossmann-fold-bearing subdomain III of GephE•The molybdenum-binding site is in close proximity to the bound nucleotide•A mutation in an active-site aspartate leads to molybdenum cofactor deficiency Structures of the C-terminal domain of the neurotransmitter-receptor anchoring protein gephyrin in complex with different nucleotides and metals by Kasaragod and Schindelin provide important insights into the evolutionarily conserved deadenylation and metal insertion steps catalyzed by this moonlighting protein during molybdenum cofactor biosynthesis.