title: Crystal structure of RumA, an iron-sulfur cluster containing E. coli ribosomal RNA 5-methyluridine methyltransferase.
abstract: RumA catalyzes transfer of a methyl group from S-adenosylmethionine (SAM) specifically to uridine 1939 of 23S ribosomal RNA in Escherichia coli to yield 5-methyluridine. We determined the crystal structure of RumA at 1.95 A resolution. The protein is organized into three structural domains: The N-terminal domain contains sequence homology to the conserved TRAM motif and displays a five-stranded beta barrel architecture characteristic of an oligosaccharide/oligonucleotide binding fold. The central domain contains a [Fe(4)S(4)] cluster coordinated by four conserved cysteine residues. The C-terminal domain displays the typical SAM-dependent methyltransferase fold. The catalytic nucleophile Cys389 lies in a motif different from that in DNA 5-methylcytosine methyltransferases. The electrostatic potential surface reveals a predominately positively charged area that covers the concave surface of the first two domains and suggests an RNA binding mode. The iron-sulfur cluster may be involved in the correct folding of the protein or may have a role in RNA binding.
authors.affiliation: Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94107 USA.
authors.forename: Tom T
authors.initials: TT
authors.lastname: Lee
authors.forename: Sanjay
authors.initials: S
authors.lastname: Agarwalla
authors.forename: Robert M
authors.initials: RM
authors.lastname: Stroud
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000201:enzymology*; D008780:Methyltransferases / Q000737:chemistry* / Q000378:metabolism; D008969:Molecular Sequence Data; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012335:RNA, Ribosomal / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D012335:RNA, Ribosomal; C093591:RumA protein, Bacteria; D008780:Methyltransferases