title: Analysis of a nucleotide-binding site of 5-lipoxygenase by affinity labelling: binding characteristics and amino acid sequences.
abstract: 5-Lipoxygenase (5LO) catalyses the first two steps in the biosynthesis of leukotrienes, which are inflammatory mediators derived from arachidonic acid. 5LO activity is stimulated by ATP; however, a consensus ATP-binding site or nucleotide-binding site has not been found in its protein sequence. In the present study, affinity and photoaffinity labelling of 5LO with 5'-p-fluorosulphonylbenzoyladenosine (FSBA) and 2-azido-ATP showed that 5LO bound to the ATP analogues quantitatively and specifically and that the incorporation of either analogue inhibited ATP stimulation of 5LO activity. The stoichiometry of the labelling was 1.4 mol of FSBA/mol of 5LO (of which ATP competed with 1 mol/mol) or 0.94 mol of 2-azido-ATP/mol of 5LO (of which ATP competed with 0.77 mol/mol). Labelling with FSBA prevented further labelling with 2-azido-ATP, indicating that the same binding site was occupied by both analogues. Other nucleotides (ADP, AMP, GTP, CTP and UTP) also competed with 2-azido-ATP labelling, suggesting that the site was a general nucleotide-binding site rather than a strict ATP-binding site. Ca(2+), which also stimulates 5LO activity, had no effect on the labelling of the nucleotide-binding site. Digestion with trypsin and peptide sequencing showed that two fragments of 5LO were labelled by 2-azido-ATP. These fragments correspond to residues 73-83 (KYWLNDDWYLK, in single-letter amino acid code) and 193-209 (FMHMFQSSWNDFADFEK) in the 5LO sequence. Trp-75 and Trp-201 in these peptides were modified by the labelling, suggesting that they were immediately adjacent to the C-2 position of the adenine ring of ATP. Given the stoichiometry of the labelling, the two peptide sequences of 5LO were probably near each other in the enzyme's tertiary structure, composing or surrounding the ATP-binding site of 5LO.
authors.affiliation: Whitaker Cardiovascular Institute, Boston University School of Medicine, 715 Albany Street, Boston, MA 02118, USA. yyzhang@bu.edu
authors.forename: Y Y
authors.initials: YY
authors.lastname: Zhang
authors.forename: T
authors.initials: T
authors.lastname: Hammarberg
authors.forename: O
authors.initials: O
authors.lastname: Radmark
authors.forename: B
authors.initials: B
authors.lastname: Samuelsson
authors.forename: C F
authors.initials: CF
authors.lastname: Ng
authors.forename: C D
authors.initials: CD
authors.lastname: Funk
authors.forename: J
authors.initials: J
authors.lastname: Loscalzo
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000345:Affinity Labels; D000595:Amino Acid Sequence; D001094:Arachidonate 5-Lipoxygenase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D001665:Binding Sites; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D000345:Affinity Labels; D011994:Recombinant Proteins; D000255:Adenosine Triphosphate; D001094:Arachidonate 5-Lipoxygenase