Characterization of calcium and magnesium binding domains of human 5-lipoxygenase.
Two calcium binding sites, separated by about 9.3A, present in the loops that connect the beta-sheets of N-terminal domain contain the ligating residues F14, A15, G16, D79, and D18, D19, L76, respectively. Magnesium is found to bind in regions, which are marginally different owing to the disparity in the ionic radii of Ca2+ and Mg2+. The entropy analysis on the loops of 5-lipoxygenase, implementing the wormlike chain model, explains that the N-terminal beta-barrel is well suited to accommodate calcium binding sites. The large buried side chain area of W102 (compared to W13 and W75) and comparatively smaller fraction of side chain exposed to polar atoms corroborate the calcium induced higher affinity to phosphatidylcholine (PC). However, W80 lying in close proximity of the calcium binding sites is expected to have considerable PC affinity but negligible calcium induced effect on PC binding.
Bindu
P Hima
PH
Molecular Modelling Group, Organic Chemical Sciences, Indian Institute of Chemical Technology, Hyderabad 500007, India.
Sastry
G Madhavi
GM
Sastry
G Narahari
GN
D000595:Amino Acid Sequence; D001094:Arachidonate 5-Lipoxygenase / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D006801:Humans; D008274:Magnesium / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid
D001094:Arachidonate 5-Lipoxygenase; D008274:Magnesium; D002118:Calcium