Gel-filtration and Density-gradient-centrifugation Studies of the Molecular Weights of Halobacterium Cutirubrum

1. Conditions have been established for the estimation of molecular weights of proteins by analytical gel filtration and sucrose-density-gradient centrifugation in 2.5M-potassium chloride-l M-sodium chloride; Halobacterium cutirubrum polynucleotide phosphorylase, DNA-dependent RNA polymerase and RNA-dependent RNA polymerase have been studied by these methods. 2. The RNA-dependent polymerase has also been studied by density-gradient centrifugation in the absence of salt. 3. All three proteins are of unusually low molecular weight compared with similar enzymes from non-halophilic bacteria.