title: Three new members of the serine-aspartate repeat protein multigene family of Staphylococcus aureus.
abstract: Three new genes encoding the serine-aspartate (SD) repeat-containing proteins SdrC, SdrD and SdrE were found in Staphylococcus aureus strain Newman. The SD repeats had earlier been found in the S. aureus fibrinogen-binding clumping factors ClfA and ClfB. The clfA and clfB genes encode high-molecular-mass fibrinogen-binding proteins that are anchored to the cell surface of S. aureus. The sdr genes now reported are closely linked and tandemly arrayed. The putative Sdr proteins have both organizational and sequence similarity to ClfA and ClfB. At the N-terminus, putative secretory signal sequences precede approximately 500 residue A regions. The A regions of the Sdr and Clf proteins exhibit only 20-30% residue identity when aligned with any other member of the family. The only conserved sequence is the consensus motif TYTFTDYVD. The Sdr proteins differ from ClfA and ClfB by having two to five additional 110-113 residue repeated sequences (B-motifs) located between region A and the R-region. Each B-motif contains a consensus Ca2+-binding EF-hand loop normally found in eukaryotic proteins. The structural integrity of recombinant SdrD(B1-B5) protein comprising the five B-repeats of SdrD was shown by bisANS fluorescence analysis to be Ca2+-dependent, suggesting that the EF-hands are functional. When Ca2+ was removed the structure collapsed to an unfolded conformation. The original structure was restored by addition of Ca2+. The C-terminal R-domains of the Sdr proteins contain 132-170 SD residues. These are followed by conserved wall-anchoring regions characteristic of many surface proteins of Gram-positive bacteria. The sdr locus was present in all 31 S. aureus strains from human and bovine sources tested by Southern hybridization, although in a few strains it contained two rather than three genes.
authors.affiliation: Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College, Dublin 2, Ireland.
authors.forename: Elisabet
authors.initials: E
authors.lastname: Josefsson
authors.affiliation: Institute of Biosciences and Technology, Texas Medical Center, 2121 West Holcombe Boulevard, Houston, TX 77030-3303, USA.
authors.forename: Kirk W
authors.initials: KW
authors.lastname: McCrea
authors.affiliation: Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College, Dublin 2, Ireland.
authors.forename: Deirdre Ni
authors.initials: DN
authors.lastname: Eidhin
authors.affiliation: Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College, Dublin 2, Ireland.
authors.forename: David
authors.initials: D
authors.lastname: O'Connell
authors.affiliation: Department of Biochemistry, University of Geneva, 30 quai Ernest Ansermet, 1211 Geneva 4, Switzerland.
authors.forename: Jos
authors.initials: J
authors.lastname: Cox
authors.affiliation: Institute of Biosciences and Technology, Texas Medical Center, 2121 West Holcombe Boulevard, Houston, TX 77030-3303, USA.
authors.forename: Magnus
authors.initials: M
authors.lastname: Hook
authors.affiliation: Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College, Dublin 2, Ireland.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Foster
mesh_terms: D000595:Amino Acid Sequence; D001224:Aspartic Acid / Q000737:chemistry / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics*; D002135:Calcium-Binding Proteins / Q000235:genetics; D003030:Coagulase / Q000235:genetics; D004269:DNA, Bacterial / Q000032:analysis; D008969:Molecular Sequence Data; D005810:Multigene Family; D011487:Protein Conformation; D012091:Repetitive Sequences, Nucleic Acid; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000737:chemistry / Q000235:genetics; D013211:Staphylococcus aureus / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D002135:Calcium-Binding Proteins; D003030:Coagulase; D004269:DNA, Bacterial; C118508:SdrC protein, Staphylococcus aureus; C115915:SdrD protein, Staphylococcus aureus; C118507:SdrE protein, Staphylococcus aureus; D001224:Aspartic Acid; D012694:Serine