Control of proline synthesis in Escherichia coli

Baich, Annette; Pierson, David J.

doi:10.1016/0304-4165(65)90345-4

Cited by 66 publications

(32 citation statements)

References 14 publications

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“…This is consistent with work on Escherichia coli (1) and tobacco leaves (14) that implies proline biosynthesis is limited by the rate of formation of P5C. The conversion of P5C to proline, on the other hand, seems to proceed freely in these organisms (1,14). In leaves that were wilted 8 or 16 hr before feeding the radioactive precursors, an increase in proline radioactivity was observed ( Fig.…”

Section: Discussionsupporting

confidence: 89%

Effect of Water Stress on Proline Synthesis from Radioactive Precursors

et al. 1976

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Barley (ffordeum vulgare L. var. Prior) leaves converted more '4C-glutamic acid to free proline when water-stressed than when turgid; neither decreased protein synthesis nor isotope trapping by the enlarged free proline pools found in wilted tissue seemed to account for the result. This apparent stimulation of proline biosynthesis in wilted leaves was not observed when radioactive ornithine or P5C (A1-pyrroline-5-carboxylate, an intermediate following glutamate in proline synthesis) were used as proline precursors unless proline levels were high as a result of previous water stress. We interpret this to mean that any stimulation of proline synthesis by water stress must act on P5C formation rather than its reduction to proline. Experiments showing greater apparent conversion of 14C-glutamate to proline do not unequivocally prove that proline synthesis is stimulated by water stress, as P5C feeding studies show that proline oxidation is inhibited under comparable conditions. This inhibition could account, at least in part, for increased proline labeling, and must be considered an alternate possibility.Although several plants have been reported to accumulate free proline during periods of water deficit (2,12,15,16,18) or when subjected to other stress (7, 8), the biochemical changes linking water stress and proline accumulation are not well understood. Barnett and Naylor (2) and Morris et al. (13) have observed increased incorporation of 14C-glutamic acid into proline in wilted leaves as compared to turgid leaves of Bermuda grass and turnip. This increase in radiotracer incorporation might reflect a stimulation of proline biosynthesis by water stress, but the data presented did not fully eliminate the possibility that inhibited protein synthesis might account for the results.The Bermuda grass experiment was done after a long period of drought, so that the large amount of free proline already present during "4C-glutamate feeding could have acted as a trapping pool for radioactive proline, accounting for the results in the absence of an actual increase in the rate of conversion of glutamate to proline. In this paper we describe 14C-glutamate feeding experiments designed to avoid these difficulties in interpretation, and to localize the point in the proline biosynthetic pathway at which a stress-induced stimulation would most likely occur.

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Section: Discussionsupporting

confidence: 89%

Effect of Water Stress on Proline Synthesis from Radioactive Precursors

et al. 1976

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“…The overall conversion of glutamate to A1-pyrroline-5-carboxylic acid is inhibited by proline, 3,4-dehydroproline and, to a lesser extent, by azetidine (Strecker, 1957;Baich & Pierson, I 965 ; Tristram & Thurston, I 966). Formation of A1-pyrroline-~-carboxylic acid by a proline-excreting 3,4-dehydroproline-resistant mutant had lost its sensitivity to proline (Baich & Pierson, 1965). At least the earlier enzymes of proline biosynthesis are subject to enzyme repression by the final product of the pathway (Tristram & Thurston,I 966).…”

Section: Discussionmentioning

confidence: 99%

The Activity and Specificity of the Proline Permease in Wild-type and Analogue-resistant Strains of Escherichia coli

Tristram

Neale

1968

Journal of General Microbiology

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SUMMARYThe main characteristics of the previously described proline-specific transport mechanism (permease) of Escherichia coli were confirmed in strain c4. The same permease was responsible for entry of a number of proline analogues, including 3,4-dehydroproline7 4-methyleneprolineY cis-and trans-4-chloroprolines, thiazolidine-4-carboxylic acid (thioproline) and the lower homologue, azetidine-2-carboxylic acid. These analogues also entered the cells by an exchange reaction between extracellular analogue and previously accumulated intracellular proline. Growth of the parent (c 4) strain was inhibited by 3,4-dehydroproline and azetidine-2-carboxylic acid, both of which were incorporated into cellular protein. Several classes of mutants, selected for resistance to either dehydroproline or azetidine, failed to incorporate one or both analogues into protein. Some of these mutants owed their resistance to failure to produce a functional proline permease. At least one strain, resistant to azetidine but not to dehydroproline, possessed an altered permease with little affinity for azetidine-2-carboxylic acid but still capable of transporting proline and 3,4-dehydroproline ; the permease of this strain could no longer promote exchange between intracellular proline and extracellular proline or proline analogues.

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“…In the course of our studies of N-acetylglutamate phosphokinase, it was found that extracts catalyzed a slower rate of formation of a hydroxamate from glutamate. However, it is not clear whether this is due to a glutamate y-phosphokinase which would be involved in the biosynthesis of proline (Baich & Pierson, 1965) or due to a glutamine synthetase (Ravel, Humphreys & Shive, 1965). Evidence in favour of the mechanisms of conversion of glutamate to arginine is more substantial although still lacking in detail.…”

Section: Ch Ch3mentioning

confidence: 99%