Intracellular Protein Breakdown in a Thermophile

Abstract

Protein breakdown of 5 to 7% per hr was found in nitrogen-starved cells of an unclassified prototrophic thermophilic bacillus; a similar protein-breakdown rate (6.5% per hr) was found in resting cells of Escherichia coli. In the thermophile, the rate of protein breakdown was markedly influenced by the temperature; it was maximal between 45 and 55 C, and it decreased considerably at 35 and 75 C, temperatures which are only slightly below or above the minimal and maximal growth temperatures. Growing cultures of the thermophile showed little, if any, protein breakdown, a finding similar to that of others with E. coli.

Intracellular protein breakdown in thermophilic and mesophilic fungi

“…In nongrowing fungi the rate of breakdown was found to vary between 5.2% and 6.7 %/h ( Table 2). The rate e rate of breakdown of total of protein turnover in non-growing bacterial susa 5.2% and 6.7Y%/h for all of pensions of thermophiles and mesophiles was found Lmarked difference, however, to vary between 5% and 7%/h (Mandelstam, 1958; tes of breakdown of soluble Urba, 1959;Willetts, 1967a), and was also found to philes the rate of breakdown be influenced by the temperature of the assay n was about twice the rate of (Epstein & Grossowicz, 1969). Our results show that rn, whereas in the mesophiles the rate of protein breakdown for P. duponti and of soluble protein was much P. notatum increased as the growth temperature was otein breakdown rate.…”

“…Vol. 144 nd soluble protein breakdown in In bacterial studies the radioactivity of the cells vophilic fungi was used as an index of the radioactivity of the total paration of the soluble protein protein (Epstein & Grossowicz, 1969 occurring in non-growing fungal cell suspensions (Fig. 1) and (b) that Mandelstam (1958) has shown in 28 5.2 3.9…”

“…The rapid-turnover theory was initially proposed by Allen (1953) and supported by the studies carried out by Bubela & Holdsworth (1966). More recently, however, it has been shown that the rate of protein turnover in thermophilic bacteria is the same as that found in mesophilic bacteria (Epstein & Grossowicz, 1969;Coultate & Sundaram, 1971). Growing cells generally exhibit a turnover rate of less than 3 %/h (Mandelstam, 1958), whereas much faster rates of turnover are found in non-growing cells (3-7 %/h) (Epstein & Grossowicz, 1969;Mandelstam, 1958) and sporulating cells (18-22%/h) (Spudich & Kornberg, 1968;Bernlohr, 1972).…”

“…protein in the fungi we examined accounted for only a non-growing bacteria has 10-20% of the total protein, which explains why the ber of media by removing any soluble protein breakdown rate did not greatly affect mponents such as nitrogen the breakdown rate of total protein. -Harnida, 1966;Epstein & The observation that, in the thermophilic fungi, icose or phosphate (Willetts, the rate of soluble protein breakdown is higher than )ecific mutants (Mandelstam, the rate of total protein breakdown suggests that, in the modified CDP medium order to survive at high temperatures, these fungi l for both fungi used in this have developed the capacity to rapidly resynthesize h conditions were produced the labile soluble proteins. The insoluble proteins ved from this medium (Table are associated with other cellular components and rogen or phosphate from the this may protect them from degradation.…”

The complex effect of temperature on protein degradation in sporulating Bacillus megaterium

“…These conclusions were based on the analysis of the rate of protein degradation within a series of short time intervals and are not accepted unanimously. Epstein and Grossowicz [9] found that the turnover of proteins in non-grow-ingE. coli was decreased at 45°C and that it reached its maximum value at the optimal temperature even in a thermophilic bacillus.…”