Conformational Changes of the Chromatin Subunit
Abstract
Hydrodynamic studies on monomer chromatin subunits (ν 1) as a function of ionic strength (0.7 mM to 100 mM KCl) indicate two salt-dependent conformational transitions. An abrupt transition occurs at about 7.5 mM ionic strength. Decreasing the ionic strength from 10 to 5 mM results in a decrease in s20,w of the ν 1 from 11.1 to 9.9 S. The diffusion coefficient D20,w decreases from 3.3 to 2.7 × 10-7 cm2 sec-1. The ν 1 crosslinked with formaldehyde at 10 mM ionic strength do not undergo a similar salt-dependent change in s20,w. Another transition is observed at about 1 mM ionic strength; s20,w decreases to 9.4 S and D20,w decreases to 2.2 × 10-7 cm2 sec-1. Throughout the entire salt range the molecular weight of the ν 1 remains reasonably constant, implying that salt-dependent changes in the frictional coefficient are being observed. Various hydrodynamic models are considered as possible interpretations of the observed changes in the frictional coefficient.
- Publication:
-
Proceedings of the National Academy of Science
- Pub Date:
- February 1978
- DOI:
- 10.1073/pnas.75.2.660
- Bibcode:
- 1978PNAS...75..660G