title: Molecular modelling and the biosynthesis of apolipoprotein B containing lipoproteins.
abstract: APOBEC-1 is the cytidine deaminase. We show by sequence alignment, molecular modelling and mutagenesis, that it is related in crystal structure to the cytidine deaminase of Escherichia coli (ECCDA). The two enzymes are both homodimers with composite active sites formed with loops from each monomer. In the sequence of APOBEC-1, three gaps compared to ECCDA match the size and contour of the minimal RNA substrate. We propose a model in which the asymmetric binding of one active site to the substrate cytidine which is positioned by the downstream binding of the product uridine and that this helps to target the other active site for deamination.
authors.affiliation: National Heart and Lung Institute, Imperial College School of Medicine, Hammersmith Hospital, London, UK. jscott@rpms.ac.uk
authors.forename: J
authors.initials: J
authors.lastname: Scott
authors.forename: N
authors.initials: N
authors.lastname: Navaratnam
authors.forename: C
authors.initials: C
authors.lastname: Carter
mesh_terms: D000071479:APOBEC-1 Deaminase; D000595:Amino Acid Sequence; D000818:Animals; D001055:Apolipoproteins B / Q000378:metabolism; D003198:Computer Simulation; D003564:Cytidine Deaminase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation; D004926:Escherichia coli; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D017421:Sequence Analysis; D013379:Substrate Specificity; D000098830:AICDA (Activation-Induced Cytidine Deaminase)
chemical_list: D001055:Apolipoproteins B; D000098830:AICDA (Activation-Induced Cytidine Deaminase); D000071479:APOBEC-1 Deaminase; C000605089:APOBEC1 protein, human; D003564:Cytidine Deaminase