Evidences of a natively unfolded state for the human topoisomerase IB N-terminal domain.
The N-terminal domain of human topoisomerase IB has been expressed, purified and characterized by spectroscopic techniques. CD spectra as a function of concentration and pH indicate that the domain does not possess any defined secondary structure. The protein is probably in a natively unfolded state since its denaturation curve is indicative of a non-cooperative transition. Evidence of a partially folded structure comes from the fluorescence spectrum of ANS, whose intensity increases in presence of the domain. Indication of a partial structural arrangement of the domain comes also from the endogenous fluorescence of tryptophans that is centred at 350 nm in the native and shifts to 354 nm in the fully denaturated protein. Interestingly despite the poor structural degree, as also confirmed by a predictive approach, the domain efficiently binds DNA, suggesting that the absence of a defined 3D structure has a functional meaning that permits the domain to be available for the interaction with different molecular partners.
Department of Biology, University of Rome Tor Vergata, Via Della Ricerca Scientifica, 00133, Rome, Italy.
Oscar
O
Vassallo
Silvia
S
Castelli
Ilda
I
D'Annessa
Blasco Morozzo
BM
della Rocca
Lorenzo
L
Stella
Birgitta R
BR
Knudsen
Alessandro
A
Desideri
D000595:Amino Acid Sequence; D000817:Anilino Naphthalenesulfonates / Q000737:chemistry; D001665:Binding Sites; D002942:Circular Dichroism; D004247:DNA / Q000378:metabolism; D004264:DNA Topoisomerases, Type I / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D011489:Protein Denaturation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D014364:Tryptophan / Q000737:chemistry
C515594:8-anilino-1-naphthalenesulfonic acid; D000817:Anilino Naphthalenesulfonates; D011994:Recombinant Proteins; D014364:Tryptophan; D004247:DNA; D004264:DNA Topoisomerases, Type I; C528909:TOP1 protein, human