We present a new method for rapid purification to near homogeneity of sequence specific DNA binding proteins based on magnetic separation. The method is described for the purification of the yeast transcription factor tau. DNA affinity Dynabeads (monodisperse superparamagnetic particles) specifically bind the protein in the presence of competitor DNA. By magnetic separation, wash and elution, highly enriched transcription factor preparations are obtained within minutes. In less than an hour with three cycles of adsorption, nearly homogeneous factor tau was obtained. The factor preparation contained mainly two polypeptides of 100 and 140 kDa and was fully active in transcription and DNA binding assays. This procedure should work for any high-affinity sequence-specific DNA binding protein with only minor modifications.
Restriction endonucleases are bacterial enzymes that cleave DNA at specific sites. The resulting DNA fragments may be separated electrophoretically in gel to form specific restriction patterns. In the present study, the restriction endonuclease method was successfully adapted to the analysis of the chromosomal DNA of Neisseria meningitidis. The endonucleases HindIlI and EcoRI provided optimal restriction patterns of ca. 50 well-separated lines. The pattern of each bacterial isolate was characteristic, stable, and reproducible. Despite some general similarity, the restriction patterns of the closely related B15 meningococci were surprisingly heterogeneous.
A study of 948 Norwegians including 118 matings with 429 children provided evidence that the Pg I group of pepsinogens must be coded for by more than one gene locus. At the Pg5 locus the alleles Pg5N, Pg5F and Pg5S with frequencies 0.644, 0.059 and 0.004, each code for a single electrophoretic isozyme band responsible for Pg phenotypes Pg 5, intense Pg (4) and Pg 5S, and a null-allele Pg5o with frequency 0.293. The Pg 2, Pg 3 and weak Pg 4 bands are not coded for by alleles at the Pg5 locus and differ from the Pg5 gene products in the oligopeptides split off by pepsinogen-pepsin conversion. The Pg5 alleles differ from each other in the pepsin-coding part of the gene. Intensity variations of Pg 5 have no simple genetic explanation.
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