title: Expression, crystallization and preliminary X-ray diffraction studies on the complete choline-binding domain of the major pneumococcal autolysin.
abstract: The major pneumococcal autolysin (LytA), a virulence factor of this bacterium, is composed of an amino-terminal catalytic domain plus a carboxyl-terminal choline-binding domain (ChBD). This C-terminal domain, responsible for anchorage to the cell wall, is a tandem of six imperfect 20-residue repeats whose precise ends have been difficult to establish by sequence methods. The reported crystal structure of a shortened C-terminal fragment of the protein suggested that it might contain an additional repeat and thus an additional choline-binding site (ChBS). The complete recombinant choline-binding domain of LytA has now been overexpressed in soluble form using a secreting Escherichia coli strain which facilitates purification with a higher yield. It has been crystallized at room temperature using MPD as the main precipitant. The crystals belong to space group P2(1) and diffract to beyond 3.2 A resolution on a synchrotron-radiation source. The molecular-replacement solution indicates that a new ChBS which fits the topology of the solenoid structure is formed in the N-terminal region.
authors.affiliation: Departamento de Estructura y Función de Proteínas, Centro de Investigaciones Biológicas-CSIC, C/Velázquez 144, Madrid 28006, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Fernández-Tornero
authors.forename: Alvaro
authors.initials: A
authors.lastname: Ramón
authors.forename: Concha
authors.initials: C
authors.lastname: Fernández-Cabrera
authors.forename: Guillermo
authors.initials: G
authors.lastname: Giménez-Gallego
authors.forename: Antonio
authors.initials: A
authors.lastname: Romero
mesh_terms: D001665:Binding Sites; D002794:Choline / Q000737:chemistry* / Q000378:metabolism; D003460:Crystallization; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D009238:N-Acetylmuramoyl-L-alanine Amidase / Q000096:biosynthesis / Q000737:chemistry*; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D013296:Streptococcus pneumoniae / Q000737:chemistry / Q000201:enzymology*
chemical_list: D011994:Recombinant Proteins; D009238:N-Acetylmuramoyl-L-alanine Amidase; D002794:Choline