Second-site rho mutation: genetic linkage and polyC-dependent ATPase.

Rho has been purified to homogeneity from Escherichia coli double mutant rho-115 sur-38 cells, and from rho6 and rho-115 cells. The sur-38 mutation suppresses the original rho-115 phenotype. We observe that the polyC-dependent ATPases of these three rho preparations have the same specific activities. However, the ATPase of rho from the double rho-115 sur-38 mutant is extremely heat labile, while that from rho-115 shows a heat lability intermediate between the wild type and the double mutant. Transduction analysis suggests that sur-38 is closely linked to rho-115 in the order ilv--sur-38--rho-115--metE. These data are consistent with the model that the sur-38 mutation affects the structural gene for rho.