Membrane association of the Tnp and Inh proteins of IS50R.

Using a radioimmunoassay for the IS50R proteins Tnp and Inh, we found that both proteins were present primarily in the cytoplasm, but 3 to 11% of Tnp and 3 to 5% of Inh were found in association with the inner membrane. The fractions of total Tnp and Inh that became membrane bound were unaffected by the amount of Tnp and Inh synthesized in whole cells, provided that the ratio of total Tnp to total Inh was not changed. In addition, Inh was not found in the membrane fraction in Tnp- IS50R mutants, indicating that Tnp is required for Inh localization.