1eg2

File:1eg2.gif

CRYSTAL STRUCTURE OF RHODOBACTER SPHEROIDES (N6 ADENOSINE) METHYLTRANSFERASE (M.RSRI)

OverviewOverview

DNA methylation is important in cellular, developmental and disease processes, as well as in bacterial restriction-modification systems. Methylation of DNA at the amino groups of cytosine and adenine is a common mode of protection against restriction endonucleases afforded by the bacterial methyltransferases. The first structure of an N:6-adenine methyltransferase belonging to the beta class of bacterial methyltransferases is described here. The structure of M. RSR:I from Rhodobacter sphaeroides, which methylates the second adenine of the GAATTC sequence, was determined to 1.75 A resolution using X-ray crystallography. Like other methyltransferases, the enzyme contains the methylase fold and has well-defined substrate binding pockets. The catalytic core most closely resembles the PVU:II methyltransferase, a cytosine amino methyltransferase of the same beta group. The larger nucleotide binding pocket observed in M. RSR:I is expected because it methylates adenine. However, the most striking difference between the RSR:I methyltransferase and the other bacterial enzymes is the structure of the putative DNA target recognition domain, which is formed in part by two helices on an extended arm of the protein on the face of the enzyme opposite the active site. This observation suggests that a dramatic conformational change or oligomerization may take place during DNA binding and methylation.

About this StructureAbout this Structure

1EG2 is a Single protein structure of sequence from Rhodobacter sphaeroides. Full crystallographic information is available from OCA.

ReferenceReference

Structure of RsrI methyltransferase, a member of the N6-adenine beta class of DNA methyltransferases., Scavetta RD, Thomas CB, Walsh MA, Szegedi S, Joachimiak A, Gumport RI, Churchill ME, Nucleic Acids Res. 2000 Oct 15;28(20):3950-61. PMID:11024175 Page seeded by OCA on Fri May 2 15:03:23 2008