A RANDOM FLIGHT CHAIN MODEL FOR THE TETHER OF THE SHAKER K+ CHANNEL INACTIVATION DOMAIN

Rapid inactivation of Shaker Kt channels occurs when a domain in the a mino terminal region of the channel protein blocks the pore. Some part of the sequence between the inactivating domain and the first transme mbrane segment may form a flexible tether, We consider the possibility that the tether has no secondary structure, but is rather a polypepti de random coil. The local concentration of the tethered inactivation d omain and the dependence of the inactivation rate on chain length can then be calculated by using the jacobson-Stockmayer equation. A chain of 30-100 amino acids is consistent with the sensitivity of the inacti vation rate to chain length mutations.