Differential feeding-related regulation of ubiquitin and calbindin9kDa in rat duodenum.
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 midnight to 8.30 a.m., the ubiquitin concentration was specifically higher at 10 pm than at 10 a.m. (11.2 +/- 0.7 and 7.7 +/- 0.8 nmol per g wet weight, respectively, P < 0.02), whereas calbindin9kDa tended towards an opposite variation (18.0 +/- 1.9 and 21.8 +/- 1.7 nmol per g, respectively). Based on its unusually high abundance and novel feeding-related variations, ubiquitin must have an important functional role in the rat duodenum which is distinctly regulated from the calcium transport-associated role of calbindin9kDa.
Department of Biochemistry, University of Otago, Dunedin, New Zealand.
M J
MJ
Hubbard
A
A
Carne
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D064026:Calbindins; D002852:Chromatography, Ion Exchange; D004386:Duodenum / Q000378:metabolism*; D004435:Eating; D015870:Gene Expression; D008969:Molecular Sequence Data; D051381:Rats; D064030:S100 Calcium Binding Protein G / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D014452:Ubiquitins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*
D064026:Calbindins; D064030:S100 Calcium Binding Protein G; D014452:Ubiquitins