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A mutant rho ATPase from Escherichia coli that is temperature-sensitive in the presence of RNA

✍ Scribed by Kent, Rachel B. ;Guterman, Sonia K.

Publisher: Springer
Year: 1981
Tongue: English
Weight: 566 KB
Volume: 181
Category: Article
ISSN: 0026-8925
DOI: 10.1007/bf00425613

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✦ Synopsis

The Escherichia coli mutant rho-I15 suppresses lac operon polarity conferred by the lacZ: :IS1 insertion MS319. The ATPase activity of purified rho-115 protein was maximal at 40 ° C, in contrast to 45 ° C for rho +. At higher temperatures (50 ° C, 55 ° C), the fractions of activities at maximal temperature were consistently lower for rho-115 compared to rho +. The 30minute time course of rho-115 ATP hydrolysis was linear at 37 ° C but at 45 ° C the linear kinetics of hydrolysis reached a plateau between 10 and 15 minutes. The 30-minute time courses for rho ÷ were linear at both 37°C and 45°C. The rho-115 and rho ÷ ATPase activities were equally heat-stable during preincubation at 45 ° C in buffer. Inclusion of ATP during preincubation protected these rho proteins from inactivation to the same extent. The presence of polyC during preincubation protected rho + activity but produced substantial inactivation of rho-115 ATPase. The presence of polyU during preincubation gave similar results. Concentrations of polyC between 625 ng/ml and 100 gg/ml yielded the same extent of rho-115 ATPase inactivation during preincubation at 45 ° C. Thermal inactivation of rho-115 ATPase by polyC was halted by shifting preincubation temperature from 45 ° C to 35 ° C, indicating that polyC-induced destabilization of rho-115 was irreversible.

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