title: Tight association of N-terminal and catalytic subunits of rabbit 12/15-lipoxygenase is important for protein stability and catalytic activity.
abstract: 12/15-Lipoxygenases (12/15-LOXs) have been implicated in inflammatory and hyperproliferative diseases but the structural biology of these enzymes is not well developed. Most LOXs constitute single polypeptide chain proteins that fold into a two-domain structure. In the crystal structure the two domains are tightly associated, but small angle X-ray scattering data and dynamic fluorescence studies suggested a high degree of structural flexibility involving movement of the N-terminal domain relative to catalytic subunit. When we inspected the interdomain interface we have found a limited number of side-chain contacts which are involved in interactions of these two structural subunits. One of such contact points involves tyrosine 98 of N-terminal domain. This aromatic amino acid is invariant in vertebrate LOXs regardless of overall sequence identity. To explore in more detail the role of aromatic interactions in interdomain association we have mutated Y98 to various residues and quantified the structural and functional consequences of these alterations. We have found that loss of an aromatic moiety at position 98 impaired the catalytic activity and membrane binding capacity of the mutant enzymes. Although CD and fluorescence emission spectra of wild-type and mutant enzyme species were indistinguishable, the mutation led to enlargement of the molecular shape of the enzyme as detected by analytic gel filtration and this structural alteration was shown to be associated with a loss of protein thermal stability. The possible role of tight interdomain association for the enzyme's structural performance is discussed.
authors.affiliation: Institute of Biochemistry, Charité-Universitätsmedizin Berlin, Berlin, Germany. igor_ivanov@gmx.de
authors.forename: Igor
authors.initials: I
authors.lastname: Ivanov
authors.forename: Almerinda
authors.initials: A
authors.lastname: Di Venere
authors.forename: Thomas
authors.initials: T
authors.lastname: Horn
authors.forename: Patrick
authors.initials: P
authors.lastname: Scheerer
authors.forename: Eleonora
authors.initials: E
authors.lastname: Nicolai
authors.forename: Sabine
authors.initials: S
authors.lastname: Stehling
authors.forename: Constanze
authors.initials: C
authors.lastname: Richter
authors.forename: Ewa
authors.initials: E
authors.lastname: Skrzypczak-Jankun
authors.forename: Giampiero
authors.initials: G
authors.lastname: Mei
authors.forename: Mauro
authors.initials: M
authors.lastname: Maccarrone
authors.forename: Hartmut
authors.initials: H
authors.lastname: Kühn
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001092:Arachidonate 12-Lipoxygenase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001093:Arachidonate 15-Lipoxygenase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D055162:Biocatalysis; D020134:Catalytic Domain / Q000235:genetics*; D002462:Cell Membrane; D002850:Chromatography, Gel; D002942:Circular Dichroism; D003001:Cloning, Molecular; D004795:Enzyme Stability; D004926:Escherichia coli; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010957:Plasmids; D017434:Protein Structure, Tertiary; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D014169:Transformation, Bacterial; D014443:Tyrosine / Q000737:chemistry / Q000378:metabolism*
chemical_list: C475064:12-15-lipoxygenase; D011993:Recombinant Fusion Proteins; D014443:Tyrosine; D001092:Arachidonate 12-Lipoxygenase; D001093:Arachidonate 15-Lipoxygenase