Differential feeding-related regulation of ubiquitin and calbindin9kDa in rat duodenum.

Abstract

Analyses of the calcium-binding protein, calbindin9kDa, purified to apparent homogeneity (SDS-PAGE) from rat duodenum, revealed variable contamination by two other 9 kDa proteins (up to 0.2 mol equivalent each) which were identified as ubiquitin and its C-terminal variant, des-Gly-Gly-ubiquitin. We found that the co-purification of these proteins did not reflect a tight molecular interaction but instead their unexpectedly similar physical characteristics in nondenaturing conditions. Like calbindin9kDa, free ubiquitin was abundant (1% and 0.4% of soluble protein, respectively) in duodenum mucosa of 7-8-week-old rats and its concentration varied daily and with feeding status. In rats fed from ..