Biochemical identification of K14 in sturgeon. 2D-PAGE of cytoskeletal proteins extracted from sturgeon skin (a), stomach (b) and intestine (c). Isoelectric focusing (IEF) was used in the first dimension, in the second dimension we applied SDS-PAGE. Bovine serum albumin (B) and rabbit α-actin (A) were added to the samples as marker proteins. E, epidermal keratins; S, simple keratins. (a-c) Coomassie Blue stained gels, showing the polypeptide patterns, which were subsequently used for complementary keratin blot-binding (CKBB) assays. (a'-c') CKBB test employing biotinylated human keratin K18, thereby identifying type II keratins (II). (a"-c") CKBB assay using biotinylated human keratin K8 which identifies type I keratins (I). Note that the K14 spot is not present as a major component in intestine or stomach and that both tissues express a mixture of E and S keratins.