The universal Kae1 protein and the associated Bud32 kinase (PRPK), a mysterious protein couple probably essential for genome maintenance in Archaea and Eukarya.
The similarities between essential molecular mechanisms in Archaea and Eukarya make it possible to discover, using comparative genomics, new fundamental mechanisms conserved between these two domains. We are studying a complex of two proteins conserved in Archaea and Eukarya whose precise biological role and biochemical function remain unknown. One of them is a universal protein known as Kae1 (kinase-asociated endopeptidase 1). The second protein is a serine/threonine kinase corresponding to the proteins Bud32 in Saccharomyces cerevisiae and PRPK (p53-related protein kinase) in humans. The genes encoding the archaeal orthologues of Kae1 and PRPK are either contiguous or even fused in many archaeal genomes. In S. cerevisiae, Kae1 and Bud32 (PRPK) belong to a chromatin-associated complex [KEOPS (kinase, endopeptidase and other proteins of small size)/EKC (endopeptidase-like kinase chromatin-associated)] that is essential for telomere elongation and transcription of essential genes. Although Kae1 is annotated as O-sialoglycoprotein endopeptidase in most genomes, we found that the Kae1 protein from Pyrococcus abyssi has no protease activity, but is an atypical DNA-binding protein with an AP (apurinic) lyase activity. The structure of the fusion protein from Methanocaldococcus jannaschii revealed that Kae1 maintains the ATP-binding site of Bud32 [corrected] in an inactive configuration. We have in fact found that Kae1 inhibits the kinase activity of Bud32 (PRPK) in vitro. Understanding the precise biochemical function and biological role of these two proteins (which are probably essential for genome maintenance) remains a major challenge.
Hecker
Arnaud
A
Université Paris-Sud, Institut de Génétique et Microbiologie, IFR115, UMR8621-CNRS, 91405 Orsay Cedex, France.
Graille
Marc
M
Madec
Edwige
E
Gadelle
Danièle
D
Le Cam
Eric
E
van Tilbergh
Herman
H
Forterre
Patrick
P
D000595:Amino Acid Sequence; D001105:Archaea / Q000235:genetics* / Q000378:metabolism*; D019843:Archaeal Proteins / Q000378:metabolism*; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D005057:Eukaryotic Cells / Q000378:metabolism*; D020745:Genome, Archaeal / Q000235:genetics*; D008969:Molecular Sequence Data; D011494:Protein Kinases / Q000737:chemistry / Q000378:metabolism*; D017433:Protein Structure, Secondary; D043903:Pyrococcus abyssi / Q000201:enzymology
D019843:Archaeal Proteins; D004268:DNA-Binding Proteins; D011494:Protein Kinases; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase