title: Biochemical Roles for Conserved Residues in the Bacterial Fatty Acid-binding Protein Family.
abstract: Fatty acid kinase (Fak) is a ubiquitous Gram-positive bacterial enzyme consisting of an ATP-binding protein (FakA) that phosphorylates the fatty acid bound to FakB. In Staphylococcus aureus, Fak is a global regulator of virulence factor transcription and is essential for the activation of exogenous fatty acids for incorporation into phospholipids. The 1.2-Å x-ray structure of S. aureus FakB2, activity assays, solution studies, site-directed mutagenesis, and in vivo complementation were used to define the functions of the five conserved residues that define the FakB protein family (Pfam02645). The fatty acid tail is buried within the protein, and the exposed carboxyl group is bound by a Ser-93-fatty acid carboxyl-Thr-61-His-266 hydrogen bond network. The guanidinium of the invariant Arg-170 is positioned to potentially interact with a bound acylphosphate. The reduced thermal denaturation temperatures of the T61A, S93A, and H266A FakB2 mutants illustrate the importance of the hydrogen bond network in protein stability. The FakB2 T61A, S93A, and H266A mutants are 1000-fold less active in the Fak assay, and the R170A mutant is completely inactive. All FakB2 mutants form FakA(FakB2)2 complexes except FakB2(R202A), which is deficient in FakA binding. Allelic replacement shows that strains expressing FakB2 mutants are defective in fatty acid incorporation into phospholipids and virulence gene transcription. These conserved residues are likely to perform the same critical functions in all bacterial fatty acid-binding proteins.
authors.affiliation: From the Departments of Infectious Diseases and.
authors.forename: Tyler C
authors.initials: TC
authors.lastname: Broussard
authors.affiliation: Structural Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105.
authors.forename: Darcie J
authors.initials: DJ
authors.lastname: Miller
authors.affiliation: From the Departments of Infectious Diseases and.
authors.forename: Pamela
authors.initials: P
authors.lastname: Jackson
authors.affiliation: Structural Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105.
authors.forename: Amanda
authors.initials: A
authors.lastname: Nourse
authors.affiliation: Structural Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105.
authors.forename: Stephen W
authors.initials: SW
authors.lastname: White
authors.affiliation: From the Departments of Infectious Diseases and Charles.rock@stjude.org.
authors.forename: Charles O
authors.initials: CO
authors.lastname: Rock
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D017124:Conserved Sequence; D050556:Fatty Acid-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D005227:Fatty Acids / Q000737:chemistry; D015870:Gene Expression; D006860:Hydrogen Bonding; D008958:Models, Molecular; D010766:Phosphorylation; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D055550:Protein Stability; D013211:Staphylococcus aureus / Q000235:genetics / Q000378:metabolism; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids; D037521:Virulence Factors
keywords: Staphylococcus aureus (S. aureus); crystal structure; fatty acid; fatty acid kinase; fatty acid-binding protein; site-directed mutagenesis