Determinants of oligomerization of the bifunctional protein DCoHalpha and the effect on its enzymatic and transcriptional coactivator activities.
DCoH and DCoHalpha are bifunctional proteins that function as 4a-hydroxytetrahydrobiopterin dehydratases and as coactivators of HNF1alpha-dependent transcription. Although these isoforms share sequence and structural similarity and equivalent enzyme activities, DCoH is a hyperstable tetramer whereas DCoHalpha readily forms dimers. Differences in quaternary structure affect the formation of the DCoH(alpha):HNF1alpha complex. Because the interface used to bind HNF1alpha is masked in tetrameric DCoH, the DCoH:HNF1alpha complex is only formed in vivo, presumably by co-translational folding. Conversely, the DCoHalpha:HNF1alpha complex readily forms in vitro. We identified residues in DCoHalpha that differed from those in the dimer-dimer interface of tetrameric DCoH. Mutating these residues altered the quaternary state and concomitantly the ability of the mutated proteins to affect HNF1alpha-dependent DNA binding. Our results indicate that three residues, Asn61, Gln45, and Lys98 in DCoHalpha play a role in oligomeric flexibility, which enables DCoHalpha to more readily interact with HNF1alpha and increase DNA binding.
Hevel
Joan M
JM
Department of Chemistry and Biochemistry, Utah State University, 0300 Old Main Hill, Logan, UT 84322, USA. joanie.hevel@usu.edu
Pande
Priyadarshini
P
Viera-Oveson
Sandra
S
Sudweeks
Trina J
TJ
Jaffree
Layla S
LS
Hansen
Christina M
CM
Ayling
June E
JE
D030161:Avian Proteins / Q000737:chemistry* / Q000378:metabolism*; D004247:DNA / Q000737:chemistry*; D004789:Enzyme Activation; D009687:Nuclear Proteins / Q000737:chemistry* / Q000378:metabolism*; D013379:Substrate Specificity; D014157:Transcription Factors / Q000737:chemistry* / Q000378:metabolism*; D015533:Transcriptional Activation / Q000502:physiology*
D030161:Avian Proteins; D004247:DNA; D009687:Nuclear Proteins; D014157:Transcription Factors; C424685:PCBD2 protein, chicken