TliP measurement of fractional synthesis(FSR)and degradation ra"t-H (FDR) assumes the measured specific radioactivities of tracer amino acids, usually determined in either plasma or t i .sues, are similai to the speci fie radioactivities of the actual precursor pool for protein synthesis, aminoacylated tRNA Further, it is assumed amino acids arising from protein turnover are not recycled back to protein synthesis. In order t ; i pst these assumptions a mechanistic, theoretical model of prot ein turnover f or a nongrowing 30g mouse has been developed using 'V ieucine in a flooding dose to measure FSR and H leucirie in prelabeled protein to measure FDR. The model re nt. ist s o E three protein pools turning over at fast (49unno les leu, t!.. =1 . 2hr . ) , medium (440umoles leu, t1/2 = 6hr . ) or w(490urnoles leu, t.;:=24hr - ) rates and small (0 .13umoles L eu and large(4.lumoles leu) amino acid pools which exchange ami iv- acids. The flow of amino acids from the protein pools t c lie smal 1 precursor pool determines the amount of rHoyci ing. The rates of arnino acid flow between pools and pL'i. s i z es were determined by systematical ly changing the ratti or poo 1 size of interest and measuring its influence on FPR estimates. The size and rate of the slow protein turnover p< o l and the rate of exchange of amino acid between the smal1 and large amino acid pools had little influence on FSR. Therefore, measurement of fluxes between the two amino acid slols and of a slow turnovei protein pool may be unimportant determining FSR. The model helps ident ify measurements to determining accurate rates of protein turnover.
|Original language||English (US)|
|State||Published - 1996|
ASJC Scopus subject areas
- Agricultural and Biological Sciences (miscellaneous)
- Biochemistry, Genetics and Molecular Biology(all)
- Cell Biology