title: The X-ray structure of a recombinant major urinary protein at 1.75 A resolution. A comparative study of X-ray and NMR-derived structures.
abstract: Major urinary proteins belong to the lipocalin family and are present in the urine of rodents as an ensemble of isoforms with pheromonal activity. The crystal structure of a recombinant mouse MUP (rMUP) was solved by the molecular-replacement technique and refined to an R factor and R(free) of 20 and 26.5%, respectively, at 1.75 A resolution. The structure was compared with an NMR model and with a crystallographic structure of the wild-type form of the protein. The crystal structures determined in different space groups present significantly smaller conformational differences amongst themselves than in comparison with NMR models. Some, but not all, of the conformational differences between the crystal and solution structures can be explained by the influence of crystallographic contacts. Most of the differences between the NMR and X-ray structures were found in the N-terminus and loop regions. A number of side chains lining the hydrophobic pocket of the molecule are more tightly packed in the NMR structure than in the crystallographic model. Surprisingly, clear and continuous electron density for a ligand was observed inside the hydrophobic pocket of this recombinant protein. Conformation of the ligand modelled inside the density is coherent with the results of recent NMR experiments.
authors.affiliation: Laboratório Nacional de Luz Síncrotron, Caixa Postal 6192, CEP 13084-971 Campinas, SP, Brazil.
authors.forename: P R
authors.initials: PR
authors.lastname: Kuser
authors.forename: L
authors.initials: L
authors.lastname: Franzoni
authors.forename: E
authors.initials: E
authors.lastname: Ferrari
authors.forename: A
authors.initials: A
authors.lastname: Spisni
authors.forename: I
authors.initials: I
authors.lastname: Polikarpov
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry; D017124:Conserved Sequence; D003460:Crystallization; D018360:Crystallography, X-Ray; D054835:Lipocalin 1; D009682:Magnetic Resonance Spectroscopy; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry*; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid
chemical_list: D002352:Carrier Proteins; C518449:Lcn1 protein, rat; D054835:Lipocalin 1; D011506:Proteins; D011994:Recombinant Proteins; C035737:major urinary proteins