title: The structure of a haemopexin-fold protein from cow pea (Vigna unguiculata) suggests functional diversity of haemopexins in plants.
abstract: The haemopexin fold is present in almost all life forms and is utilized for carrying out diverse physiological functions. The structure of CP4, a haemopexin-fold protein from cow pea (Vigna unguiculata), was determined at 2.1 Å resolution. The protein exists as a monomer both in solution and in the crystal. The structure revealed a typical four-bladed β-propeller topology. The protein exhibits 42% sequence similarity to LS-24 from Lathyrus sativus, with substantial differences in the surface-charge distribution and in the oligomeric state. A structure-based sequence analysis of haemopexin-fold proteins of plant and mammalian origin established a sequence signature associated with the haemopexin motif. This signature sequence enabled the identification of other proteins with possible haemopexin-like topology of both plant and animal origin. Although CP4 shares a structural fold with LS-24 and other haemopexins, biochemical studies indicated possible functional differences between CP4 and LS-24. While both of these proteins exhibit spermine-binding potential, CP4 does not bind to haem, unlike LS-24.
authors.affiliation: National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, India.
authors.forename: Vineet
authors.initials: V
authors.lastname: Gaur
authors.forename: Veenu
authors.initials: V
authors.lastname: Chanana
authors.forename: Abha
authors.initials: A
authors.lastname: Jain
authors.forename: Dinakar M
authors.initials: DM
authors.lastname: Salunke
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001483:Base Sequence; D002138:Calibration; D017124:Conserved Sequence; D003460:Crystallization; D018360:Crystallography, X-Ray / Q000379:methods; D019281:Dimerization; D007887:Fabaceae / Q000378:metabolism*; D006418:Heme / Q000378:metabolism; D006466:Hemopexin / Q000737:chemistry* / Q000378:metabolism; D006868:Hydrolysis; D057927:Hydrophobic and Hydrophilic Interactions; D027807:Lathyrus / Q000378:metabolism; D046911:Macromolecular Substances / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D018532:Pisum sativum / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D010944:Plants / Q000378:metabolism*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry; D020543:Proteome / Q000032:analysis; D012015:Reference Standards; D012639:Seeds / Q000737:chemistry; D020539:Sequence Analysis, Protein; D017386:Sequence Homology, Amino Acid; D013096:Spermine / Q000378:metabolism
chemical_list: D046911:Macromolecular Substances; D010940:Plant Proteins; D021122:Protein Subunits; D020543:Proteome; D013096:Spermine; D006418:Heme; D006466:Hemopexin