title: Rubisco in complex with Rubisco large subunit methyltransferase.
abstract: SET domain protein lysine methyltransferases (PKMT) are a structurally unique class of enzymes that catalyze the specific methylation of lysine residues in a number of different substrates. Especially histone-specific SET domain PKMTs have received widespread attention because of their roles in the regulation of epigenetic gene expression and the development of some cancers. Rubisco large subunit methyltransferase (RLSMT) is a chloroplast-localized SET domain PKMT responsible for the formation of trimethyl-lysine-14 in the large subunit of Rubisco, an essential photosynthetic enzyme. Here, we have used cryoelectron microscopy to produce an 11-A density map of the Rubisco-RLSMT complex. The atomic model of the complex, obtained by fitting crystal structures of Rubisco and RLSMT into the density map, shows that the extensive contact regions between the 2 proteins are mainly mediated by hydrophobic residues and leucine-rich repeats. It further provides insights into potential conformational changes that may occur during substrate binding and catalysis. This study presents the first structural analysis of a SET domain PKMT in complex with its intact polypeptide substrate.
authors.affiliation: Department of Cell Biology and Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02115, USA. raunser@mpidortmund.mpg.de
authors.forename: Stefan
authors.initials: S
authors.lastname: Raunser
authors.forename: Roberta
authors.initials: R
authors.lastname: Magnani
authors.forename: Zhong
authors.initials: Z
authors.lastname: Huang
authors.forename: Robert L
authors.initials: RL
authors.lastname: Houtz
authors.forename: Raymond C
authors.initials: RC
authors.lastname: Trievel
authors.forename: Pawel A
authors.initials: PA
authors.lastname: Penczek
authors.forename: Thomas
authors.initials: T
authors.lastname: Walz
mesh_terms: D018360:Crystallography, X-Ray; D011495:Histone-Lysine N-Methyltransferase / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D007700:Kinetics; D008854:Microscopy, Electron; D008958:Models, Molecular; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D012273:Ribulose-Bisphosphate Carboxylase / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D021122:Protein Subunits; D011495:Histone-Lysine N-Methyltransferase; D012273:Ribulose-Bisphosphate Carboxylase