Premium
Proteins tightly bound to DNA and DNA‐synthesizing activity of nucleoids from Escherichia coli
Author(s) -
Gaziev A. I.,
Fomenko Ludmila A.,
Zakrzhevskaya Dina T.,
Petrov S. I.
Publication year - 1986
Publication title -
journal of basic microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.58
H-Index - 54
eISSN - 1521-4028
pISSN - 0233-111X
DOI - 10.1002/jobm.3620260408
Subject(s) - nucleoid , dna , escherichia coli , urea , biochemistry , chemistry , sodium , centrifugation , molecular mass , microbiology and biotechnology , biology , enzyme , gene , organic chemistry
Membrane‐attached nucleoids were isolated from E. coli and separated from proteins by 2 m NaCl. Desintegration of such nucleoids by ultrasound and subsequent centrifugation resulted in the formation of two fractions: a sediment (fraction I) and a supernatant (fraction II). The protein:DNA ratio of fraction I was equal to 27 and was different from that to fraction II (2.6). More than 70% of the proteins not dissociating at 2 m NaCl and bound to DNA of both fractions were polypeptides with molecular weights (Mw) of 31,000–23,000 daltons (31–23 Kdal). After pulse labelling of the cells with [ 3 H]‐thymidine, the specific radioactivity of newly synthesized DNA associated with fraction I was shown to be considerably higher than that of fraction II. The analysis of DNA‐synthesizing activities in fractions I and II showed that both nucleoid fractions contained DNA polymerase I. After dissolving the two fractions in 8 m urea – 0.15% sodium dodecylsulphate (SDS) they were chromatographed on hydroxyapatite. DNA‐protein complexes were obtained that did not dissociate at 4 m guanidine. HCI – 5 m urea and 1% SDS. The main protein of the complexes was a 31 Kdal polypeptide tightly bound to DNA.