It is proposed to study the polymerization or depolymerization of microtubule protein (tubulin) as well as the turnover of this morphogenic and motility related protein in normal and virally transformed tissue culture cell types. Specifically it is the objective of this study to determine whether or not viral transformation, which results in dramatic alterations in cellular morphology and motility, is accompanied by an alteration in the size of the microtubule system as measured by quantitating the percentage of the microtubule protein present as intact microtubules and as soluble protein. Furthermore, a determination of the turnover rate of this protein in normal and transformed cells, utilizing high resolution ultrathin slab polyacrylamide gel electrophoresis and partially purified microtubule proteins will be undertaken. This latter is designed to separate the role of polymerization from synthesis and degradation in changing function of microtubules during transformation. Secondarily, information concerning the turnover of the contractile protein actin in normal and transformed cells will also be obtained.