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CRYSTAL STRUCTURE OF HUMAN NMN/NAMN ADENYLYL TRANSFERASE COMPLEXED WITH TIAZOFURIN ADENINE DINUCLEOTIDE (TAD)CRYSTAL STRUCTURE OF HUMAN NMN/NAMN ADENYLYL TRANSFERASE COMPLEXED WITH TIAZOFURIN ADENINE DINUCLEOTIDE (TAD)
Structural highlights
Disease[NMNA1_HUMAN] Defects in NMNAT1 are the cause of Leber congenital amaurosis 9 (LCA9) [MIM:608553]. A severe dystrophy of the retina, typically becoming evident in the first years of life. Visual function is usually poor and often accompanied by nystagmus, sluggish or near-absent pupillary responses, photophobia, high hyperopia and keratoconus.[1] [2] [3] [4] Function[NMNA1_HUMAN] Catalyzes the formation of NAD(+) from nicotinamide mononucleotide (NMN) and ATP. Can also use the deamidated form; nicotinic acid mononucleotide (NaMN) as substrate with the same efficiency. Can use triazofurin monophosphate (TrMP) as substrate. Also catalyzes the reverse reaction, i.e. the pyrophosphorolytic cleavage of NAD(+). For the pyrophosphorolytic activity, prefers NAD(+) and NAAD as substrates and degrades NADH, nicotinic acid adenine dinucleotide phosphate (NHD) and nicotinamide guanine dinucleotide (NGD) less effectively. Fails to cleave phosphorylated dinucleotides NADP(+), NADPH and NAADP(+). Protects against axonal degeneration following mechanical or toxic insults.[5] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedNicotinamide/nicotinate mononucleotide (NMN/ NaMN)adenylyltransferase (NMNAT) is an indispensable enzyme in the biosynthesis of NAD(+) and NADP(+). Human NMNAT displays unique dual substrate specificity toward both NMN and NaMN, thus flexible in participating in both de novo and salvage pathways of NAD synthesis. Human NMNAT also catalyzes the rate-limiting step of the metabolic conversion of the anticancer agent tiazofurin to its active form tiazofurin adenine dinucleotide (TAD). The tiazofurin resistance is mainly associated with the low NMNAT activity in the cell. We have solved the crystal structures of human NMNAT in complex with NAD, deamido-NAD, and a non-hydrolyzable TAD analogue beta-CH(2)-TAD. These complex structures delineate the broad substrate specificity of the enzyme toward both NMN and NaMN and reveal the structural mechanism for adenylation of tiazofurin nucleotide. The crystal structure of human NMNAT also shows that it forms a barrel-like hexamer with the predicted nuclear localization signal sequence located on the outside surface of the barrel, supporting its functional role of interacting with the nuclear transporting proteins. The results from the analytical ultracentrifugation studies are consistent with the formation of a hexamer in solution under certain conditions. Structure of human nicotinamide/nicotinic acid mononucleotide adenylyltransferase. Basis for the dual substrate specificity and activation of the oncolytic agent tiazofurin.,Zhou T, Kurnasov O, Tomchick DR, Binns DD, Grishin NV, Marquez VE, Osterman AL, Zhang H J Biol Chem. 2002 Apr 12;277(15):13148-54. Epub 2002 Jan 11. PMID:11788603[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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