title: Properties of ribosomes centrifuged in metrizamide gradients.
abstract: The banding of ribonucleoproteins in metrizamide has been characterised using yeast ribosomes as a model system. Metrizamide does not dissociate ribosomes but it can facilitate the loss of loosely bound proteins. The buoyant density of fixed ribosomes in metrizamide gradients increases dramatically in the presence of low concentrations of Mg2+, whilst high Mg2+ concentrations give rise to multiple bands of higher density. These phenomena can be explained in terms of the binding of Mg2+ to high and low affinity sites as proposed for Escherichia coli ribosomes.
mesh_terms: D002458:Cell Fractionation / Q000379:methods; D002499:Centrifugation, Density Gradient / Q000379:methods; D008274:Magnesium / Q000378:metabolism; D008793:Metrizamide; D012270:Ribosomes / Q000378:metabolism / Q000648:ultrastructure*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*
chemical_list: D008274:Magnesium; D008793:Metrizamide