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Low protein

About: Low protein is a research topic. Over the lifetime, 8139 publications have been published within this topic receiving 213225 citations.


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Journal ArticleDOI
TL;DR: The freezing point depressing activity of the Tenebrio antifreeze was less than that of fish proteins and glycoproteins at low protein concentrations but was greater at high protein concentrations.
Abstract: Proteins which produce a thermal hysteresis (difference between the freezing and melting points) in aqueous solution are well-known for their antifreeze activity in polar marine fishes. Much less is known about the biology and biochemistry of similar antifreeze proteins found in certain insects. A thermal hysteresis protein was purified from cold acclimated larvae of the beetle, Tenebrio molitor, by using ethanol fractionation, DEAE ion-exchange chromatography, gel filtration, and high-pressure liquid chromatography. The purified protein had a molecular mass of 17 000 daltons and its N terminus was lysine. The amino acid composition of the antifreeze protein contained more hydrophilic amino acids than the fish antifreezes. This is consistent with the compositions of previously purified insect thermal hysteresis proteins. However, the percentage of hydrophilic amino acids in this Tenebrio antifreeze protein was considerably less than that of other insect thermal hysteresis proteins. The freezing point depressing activity of the Tenebrio antifreeze was less than that of fish proteins and glycoproteins at low protein concentrations but was greater at high protein concentrations.

62 citations

Journal ArticleDOI
TL;DR: According to present findings, AA composition of the rumen-degraded vegetable feed residues may markedly differ, either quantitatively or qualitatively (or both), from their original AA composition.
Abstract: 1. In the previous work (Varvikko & Lindberg, 1985), 15N-labelled rapeseed (Brassica napus), barley, ryegrass (Lolium perenne) and barley straw were incubated in the rumen in nylon bags for 5, 12 and 24 h and microbial nitrogen in the residues was quantified using the feed 15N-dilution method. In the present study, residual amino acids (AA) of these feeds were analysed, and microbially corrected AA of feed origin (feed AA) were estimated as the difference between total residual AA and respective microbial AA, assuming a constant AA composition for the microbial protein. 2. In barley and barley-straw residues, and also in ryegrass incubated in the rumen for 24 h, very large enrichment by microbial N and AA-N was found. The microbial enrichment was rather small in rapeseed residues and ryegrass incubated for 5 or 12 h. During the rumen incubation, feed N and AA-N (g/kg feed dry matter (DM] decreased very clearly in all the feeds, and feed and incubation time effects were always statistically significant (P less than 0.001). 3. The slow degradation of essential (E) feed AA compared with the respective non-essential (NE) AA degradation increased the proportion of feed EAA (g/kg determined feed AA) in barley and barley-straw residues. In rapeseed and ryegrass, residual feed EAA:NEAA remained very similar to the original. Branched-chain (Br) AA tended to increase proportionally in all the feed residues, suggesting these AA to be, on average, more resistant against microbial degradation in the rumen than other AA. Similarly, lysine was clearly increased in barley residues. A rumen degradation faster than the average rate caused decreased residual feed glutamic acid in rapeseed; methionine, alanine and glycine in barley; arginine and alanine in ryegrass; and methionine, asparagine and tyrosine in barley straw. Feed and incubation time effects were significant (P less than 0.05-0.001) for feed AA (g/kg determined feed AA) grouped as EAA, BrAA or NEAA, and for most individual AA, as well as for feed AA disappearance (%) and relative amounts (%) of feed AA in the respective residual AA. 4. According to present findings, AA composition of the rumen-degraded vegetable feed residues may markedly differ, either quantitatively or qualitatively (or both), from their original AA composition. When determining the feed AA composition of nylon-bag residues, the microbial error may be very large with starchy or fibrous feeds of low protein content. The microbial AA do not, however, considerably confuse the AA determination of protein-rich feeds.

62 citations

Journal ArticleDOI
TL;DR: It is shown that persistent residual structure in the monomer of E7 is responsible for its reported anomalous electrophoretic behavior and conformational properties that could have evolved to enable protein-protein recognition of the large number of cellular binding partners reported.
Abstract: High-risk papillomaviruses are known to exert their transforming activity mainly through E7, one of their two oncoproteins. Despite its relevance, no structural information has been obtained that could explain the apparent broad binding specificity of E7. Recombinant E7 from HPV-16 purified to near homogeneity showed two species in gel filtration chromatography, one of these corresponding to a dimer with a molecular weight of 22 kDa, determined by multiangle light scattering. The E7 dimer was isolated for characterization and was shown to undergo a substantial conformational transition when changing from pH 7.0 to 5.0, with an increase in helical structure and increased solvent accessibility to hydrophobic surfaces. The protein was resistant to thermal denaturation even in the presence of SDS, and we show that persistent residual structure in the monomer is responsible for its reported anomalous electrophoretic behavior. The dimer also displays a nonglobular hydrodynamic volume based on gel filtration experiments and becomes more globular in the presence of 0.3 M guanidinium chloride, with hydrophobic surfaces becoming accessible to the solvent, as indicated by the large increase in ANS binding. At low protein concentration, dissociation of the globular E7 dimer was observed, preceding the cooperative unfolding of the structured and extended monomer. Although E7 bears properties that resemble natively unfolded polypeptides, its far-UV circular dichroism spectrum, cooperative unfolding, and exposure of ANS binding sites support a folded and extended, as opposed to disordered and fluctuating, conformation. The large increase in solvent accessibility to hydrophobic surfaces upon small pH decrease within physiological range and in mild denaturant concentrations suggests conformational properties that could have evolved to enable protein-protein recognition of the large number of cellular binding partners reported.

62 citations

Journal ArticleDOI
TL;DR: The utility of the acylhydrazone linker was validated in a proteomic search wherein aldehyde dehydrogenase-1 was selectively captured and isolated from the mouse soluble liver proteome without interfering background proteins.

62 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20227
2021298
2020300
2019278
2018308
2017306