DNA-induced secondary structure of the carboxyl-terminal domain of histone H1.
We have studied the secondary structure of the carboxyl-terminal domains of linker histone H1 subtypes H1(0) (C-H1(0)) and H1t (C-H1t), free in solution and bound to DNA, by IR spectroscopy. The carboxyl-terminal domain has little structure in aqueous solution but becomes extensively folded upon interaction with DNA. The secondary structure elements present in the bound carboxyl-terminal domain include the alpha-helix, beta-structure, turns, and open loops. The structure of the bound domain shows a significant dependence on salt concentration. In low salt (10 mm NaCl), there is a residual amount of random coil, 7% in C-H1(0) and 12% in C-H1t. In physiological salt concentrations (140 mm NaCl), the carboxyl termini become fully structured. Under these conditions, C-H1(0) contained 24% alpha-helix, 25% beta-structure, 17% open loops, and 33% turns. The latter component could include a substantial proportion of the 3(10) helix. Despite their low sequence identity (approximately 30%), the representation of the different structural motifs in C-H1t was similar to that in C-H1(0). Examination of the changes in the amide I components in the 20-80 degrees C temperature interval showed that the secondary structure of the DNA-bound C-H1t is for the most part extremely stable. The H1 carboxyl-terminal domain appears to belong to the so-called disordered proteins, undergoing coupled binding and folding.
Roque
Alicia
A
Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias, Universidad Autónoma de Barcelona, Bellaterra, Spain.
Iloro
Ibon
I
Ponte
Imma
I
Arrondo
José Luis R
JL
Suau
Pedro
P
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D055592:Biophysical Phenomena; D001703:Biophysics; D002843:Chromatin / Q000737:chemistry; D002942:Circular Dichroism; D003001:Cloning, Molecular; D004247:DNA / Q000737:chemistry*; D006657:Histones / Q000737:chemistry*; D007700:Kinetics; D051379:Mice; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D012965:Sodium Chloride / Q000494:pharmacology; D013053:Spectrophotometry; D013696:Temperature; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry
D002843:Chromatin; D006657:Histones; D014867:Water; D012965:Sodium Chloride; D004247:DNA