Non-stereoselective formation of 3 alpha,7 alpha,12 alpha,24-tetrahydroxy-5 beta-cholestan-26-oic acid during cholic acid biosynthesis

Incubation of (25RS)-, (25R)- and (25S)-3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestan-26-oic acid (THCA, 6, 6a, 6b) and (24E)-3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholest-24-en-26-oic acid (7) with rat liver mitochondria gave all four stereoisomers (9a,9b,9c,9d) of 3 alpha,7 alpha,12 alpha,24-Tetrahydroxy-5 beta-cholestan-26-oic acid (TeHCA). The corresponding 27-nor analogs (10,11) were also converted non-stereoselectively to a 1:1 mixture of the epimeric 24-hydroxy compounds (12).     

26S-ribonucleoprotein complex (26S-proteasome) directly interacts with fibrillar actin

26S-complex was purified from rat liver cells by centrifugation in sucrose gradients and ion exchange chromatography. The ability of 26S-proteasome to interact with fibrillar actin (F-actin) was examined by rapid cosidementation of these particles with F-actin in isokinetic sucrose gradients. It was shown that direct interaction occurred only at a low ATP concentration.