ISOLATION AND PRELIMINARY CHARACTERIZATION OF HISTONE H1.B ALLELIC VARIANTS FROM QUAIL ERYTHROCYTES

Our goal was to purify and characterize the allelic variants H1b1 and H1b2 of histone H1.b, one of the seven subtypes of this linker histone extracted from Japanese quail erythrocyte nuclei. These variants are revealed phenotypically as band H1.3 or part of band H1.4 by polyacryl amide gel electrophoresis (PAGE) in sodium dodecyl sulfate (SDS). All H1 subtypes together were separated from H5 by gel-permeation chromato graphy through Bio-Gel P-150. H1 was then fractionated on a column of the cation-exchange resin Amberlite CG-50 by using a shallow guanidine hydrochloride gradient, which enriched subtype H1.b together with H1. z and overlapping with subtypes H1.a and H1.b. Alternatively purificat ion of subtypes was achieved electrophoretically: total H1 fractions f rom quail with different H1 phenotypes were first resolved into sub-ty pes by PAGE in acetic acid - urea; after staining, the appropriate H1. b bands from several parallel gel pieces were excised and the histone was concentrated by PAGE in SDS. After fragmentation of H1.b in the ge l pieces with N-bromosuccinimide (NBS), PAGE in SDS indicated no diffe rence between H1b1 and H1b2 in the C-terminal ''half'' of the polypept ides. In contrast, limited digestion with endoprotease V8 from Staphyl ococcus aureus has shown that differences, probably by a few residues in length, reside in the N-terminal part of the molecule, close to the amino-terminus.