A CTP-dependent archaeal riboflavin kinase forms a bridge in the evolution of cradle-loop barrels.
Proteins of the cradle-loop barrel metafold are formed by duplication of a conserved betaalphabeta-element, suggesting a common evolutionary origin from an ancestral group of nucleic acid-binding proteins. The basal fold within this metafold, the RIFT barrel, is also found in a wide range of enzymes, whose homologous relationship with the nucleic acid-binding group is unclear. We have characterized a protein family that is intermediate in sequence and structure between the basal group of cradle-loop barrels and one family of RIFT-barrel enzymes, the riboflavin kinases. We report the structure, substrate-binding mode, and catalytic activity for one of these proteins, Methanocaldococcus jannaschii Mj0056, which is an archaeal riboflavin kinase. Mj0056 is unusual in utilizing CTP rather than ATP as the donor nucleotide, and sequence conservation in the relevant residues suggests that this is a general feature of archaeal riboflavin kinases.
Ammelburg
Moritz
M
Department of Protein Evolution, Max-Planck-Institute for Developmental Biology, 72076 Tübingen, Germany.
Hartmann
Marcus D
MD
Djuranovic
Sergej
S
Alva
Vikram
V
Koretke
Kristin K
KK
Martin
Jörg
J
Sauer
Guido
G
Truffault
Vincent
V
Zeth
Kornelius
K
Lupas
Andrei N
AN
Coles
Murray
M
D000595:Amino Acid Sequence; D001105:Archaea / Q000201:enzymology*; D003570:Cytidine Triphosphate / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid
D003570:Cytidine Triphosphate; D017853:Phosphotransferases (Alcohol Group Acceptor); C022532:riboflavin kinase