Surface hydrophobicity, arginylation and degradation of cytosol proteins from rat hepatocytes

In vitro 14C-prelabelled cytosol proteins from rat hepatocytes were incubated with [3H]arginyl-tRNA in ATP-Tris-Mg-KCl-dithioerithrol medium and arginyltransferase, subsequently treated with RNase A, and the double-labelled proteins were isolated by gel filtration. The affinity of these [3H]arginylated-14C-labelled cytosol proteins to hydrophobic surfaces was investigated with octyl-Sepharose, phenyl-Sepharose and with FPLC on phenyl-Superose (HR 5/5). All 3H/14C-ratios of the proteins in the column fractions show that arginylated proteins bind preferentially to the hydrophobic matrices: the fractions eluted first show low 3H/14C-ratios, and after addition of ethylene glycol and especially of Tween 80 the 3H/14C-ratios markedly increase. Furthermore, these arginylated proteins aggregate preferentially after incubation of the cytosol proteins for 2 h at 37 degrees C and are more rapidly degraded by endopeptidases.