Identification of a 34 Amino Acid Stretch within the C-Terminus of Histone H1 As the DNA-Condensing Domain by Site-Directed Mutagenesis†

Bharath, M. M. Srinivas ; Ramesh, Sneha ; Chandra, Nagasuma R. ; Rao, M. R. S. (2002) Identification of a 34 Amino Acid Stretch within the C-Terminus of Histone H1 As the DNA-Condensing Domain by Site-Directed Mutagenesis† Biochemistry, 41 (24). pp. 7617-7627. ISSN 0006-2960

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Official URL: http://doi.org/10.1021/bi025773+

Related URL: http://dx.doi.org/10.1021/bi025773+

Abstract

The C-terminus of histone H1 is necessary for the folding of polynucleosomal arrays into higher-order structure(s) and contains octapeptide repeats each having DNA binding S/TPKK motifs. These repeat motifs were earlier shown to mimic the DNA/chromatin-condensing properties of the C-terminus of histone H1 (Khadake, J. R., and Rao, M. R. S. (1995) Biochemistry36, 1041−1051). In the present study, we have generated a series of C-terminal mutants of rat histone H1d and studied their DNA-condensation properties. The single proline to alanine mutation in the S/TPKK motifs either singly or in combination resulted in only a 20% decrease in the DNA-condensation property of histone H1. Deletion of all the three S/TPKK motifs resulted in a 45% decrease in DNA condensation. When the three octapeptide repeats encompassing the S/TPKK motifs were deleted, there was again a 45% decrease in DNA condensation. On the other hand, when the entire 34 amino acid stretch (residue 145−178) was deleted, there was nearly a 90% decrease in DNA condensation brought about by histone H1d. Interestingly, deletion of the 10 amino acid spacer between the octapeptide repeats (residues 161−170) also reduced the DNA condensation by 70%. Deletion of the region (residues 115−141) immediately before the 34 amino acid stretch and after the globular domain and the region (residues 184−218) immediately after the 34 amino acid stretch had only a marginal effect on DNA condensation. The importance of the 34 amino acid stretch, including the 10 amino acid spacer, was also demonstrated with the recombinant histone H1d C-terminus. We have also determined the induced α-helicity of histone H1 and its various mutants in the presence of 60% trifluoroethanol, and the experimentally determined induced helical contents agree with the theoretical predictions of secondary structural elements in the C-terminus of histone H1d. Thus, we have identified a 34 amino acid stretch in the C-terminus of histone H1d as the DNA-condensing domain.

Item Type:Article
Source:Copyright of this article belongs to American Chemical Society.
Keywords:Peptides and Proteins; Genetics; Monomers; Condensation; Chemical Structure.
ID Code:117012
Deposited On:08 Apr 2021 06:43
Last Modified:08 Apr 2021 06:43

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