Showing papers on "Histone binding published in 1988"

Identification of domains involved in nuclear uptake and histone binding of protein N1 of Xenopus laevis.

Abstract: The karyophilic protein N1 (590 amino acids) is an abundant soluble protein of the nuclei of Xenopus laevis oocytes where it forms defined complexes with histones H3 and H4 The amino acid sequence of this protein, as deduced from the cDNA, reveals a putative nuclear targeting signal as well as two acidic domains which are candidates for the interaction with histones Using two different histone binding assays in vitro we have found that the deletion of the larger acidic domain reduces histone binding drastically to a residual value of approximately 15% of the complete molecule, whereas removal of the smaller acidic domain only slightly reduces histone complex formation in solution, but infers more effectively with binding to immobilized histones In the primary structure of the protein both histone-binding domains are distant from the conspicuous nuclear accumulation signal sequence (residues 531-537) close to the carboxy terminus which is very similar to the SV40 large T-antigen nuclear targeting sequence Using a series of N1 mutants altered by deletions or point mutations we show that this signal is required but not sufficient for nuclear accumulation of protein N1 The presence of an additional, more distantly related signal sequence in position 544-554 is also needed to achieve a level of nuclear uptake equivalent to that of the wild-type protein Results obtained with point mutations support the concept of two nuclear targeting sequences and emphasize the importance of specific lysine and arginine residues in these signal sequences

The double reactivity of a human monoclonal rheumatoid factor to IgG and histones is related to distinct binding sites

Abstract: The structural basis of the double reactivity of a human monoclonal rheumatoid factor (RF) with both human IgG and histones H1 and H3 was investigated by means of competitive inhibition experiments. The monoclonal RF binding to solid-phase histones was inhibited by increasing concentrations of heat-aggregated IgG. However, increasing concentrations of purified histones were almost unable to reduce the RF binding to solid-phase IgG. Inhibition of antigen binding with two murine monoclonal anti-idiotopes reacting with distinct idiotopes on the monoclonal RF indicated that the fixation to the different antigens was mediated by distinct binding sites. This result was confirmed by showing the selective sensitivity to mild acid treatment of the histone binding site but not of the IgG binding site. This report provides a structural basis for the existence of polyfunctional combining regions on a human autoantibody.