[70] Guanidination of proteins

Kimmel, Joe R.

doi:10.1016/s0076-6879(67)11072-0

Cited by 101 publications

(74 citation statements)

References 13 publications

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“…As shown in (14). A survey of earlier literature shows that though most or all c-NH2 groups of proteins are guanidinated by O-methylisourea, the a-NH2 group never reacts with this agent (32,33). Analysis of guanidinated lysozyme (Gdn-lysozyme) prepared under conditions of strong guanidination shows 0.5 lysine residue remained vs. 1.4 amine residues (Table 3); the difference is accounted for by the free a-NH2 group.…”

Section: Methodsmentioning

confidence: 99%

Role of the alpha-amino group of protein in ubiquitin-mediated protein breakdown.

Hershko¹,

Heller²,

Eytan³

et al. 1984

Proc. Natl. Acad. Sci. U.S.A.

238

139

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Previous studies suggest that the conjugation of ubiquitin to NH2 groups of proteins is required for protein breakdown. We now show that the selective modification of NH2-terminal a-NH2 groups of globin and lysozyme prevents their degradation by the ubiquitin proteolytic system from reticulocytes. The conjugation by ubiquitin of e-NH2 groups of lysine residues, usually seen in multiples, was also inhibited in a-NH2-blocked proteins. Naturally occurring N-acetylated proteins are not degraded by the ubiquitin system at a significant rate, while their nonacetylated counterparts from other species are good substrates. This suggests that one function of N'-acetylation of cellular proteins is to prevent their degradation by the ubiquitin system. a-NH2-blocked proteins can have their activity as substrates for degradation increased by incorporation of a-NH2 groups through the introduction of polyalanine side chains. Proteins in which most e-NH2 groups are blocked but the a-NH2 group is free are degraded by the ubiquitin system, but at a reduced rate. It is therefore suggested *that the exposure of a free NH2 terminus of proteins is required for degradation and probably initiates the formation of ubiquitin conjugates committed for degradation.Studies on the mode of action of an ATP-dependent proteolytic system from reticulocytes revealed a pathway for the degradation of intracellular proteins (for reviews see refs. 1 and 2). That system requires for activity the 8500-dalton polypeptide ubiquitin (Ub) (3, 4). Ub is covalently conjugated to proteins (5) by a sequence of reactions in which the COOH-terminal residue of the polypeptide is first activated by a specific Ub-activating enzyme, E1 (6, 7), and activated Ub is transferred to protein by the action of two further enzymes, E2 and E3 (8). The structure of Ub-protein conjugates has not yet been characterized sufficiently, but at least some Ub molecules bind to E-NH2 groups of lysine residues by isopeptide linkages (5,9). Proteins conjugated to multiple molecules of Ub are degraded by an ATP-dependent enzyme system that does not degrade unconjugated proteins (10). The metabolic function of the Ub proteolytic system was strongly supported by a recent study in which a mammalian cell line found to have a temperature-sensitive Ub-activating enzyme was found to be defective in degrading most of its rapidly turning over protein (11).A central problem is what features of protein structure are recognized by the Ub conjugation system for commitment to proteolysis. Since most lysine residues are exposed at the surface of most proteins, the availability of any lysine does not seem to be sufficient for specific recognition. One approach is to study the influence of the modification of specific amino groups in proteins. Other investigators have used complete blocking of protein amino groups to distinguish between Ub-dependent and Ub-independent proteolytic systems (12, 13), and the requirement for free NH2 groups has been confirmed for the Ub-dependent system. On the other ha...

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Section: Methodsmentioning

confidence: 99%

Role of the alpha-amino group of protein in ubiquitin-mediated protein breakdown.

Hershko¹,

Heller²,

Eytan³

et al. 1984

Proc. Natl. Acad. Sci. U.S.A.

238

139

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“…4, A-C). To confirm that the peptide was derived from human hsp60, we determined the number of lysines and terminal glycines present by guanidination of the peptides in question (42,43). In these experiments, O-methylisourea reacts only with lysines and terminal glycines with a predicted 42-Da increase in molecular mass occurring for every diamidomethane group added.…”

Section: Identification Of a Peptide From Hsp60 As The Dominant Qa-1-mentioning

confidence: 99%

A Peptide from Heat Shock Protein 60 Is the Dominant Peptide Bound To Qa-1 in the Absence of the MHC Class Ia Leader Sequence Peptide Qdm

Davies¹,

Kalb

Liang

et al. 2003

The Journal of Immunology

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The MHC class Ib molecule Qa-1 binds specifically and predominantly to a single 9-aa peptide (AMAPRTLLL) derived from the leader sequence of many MHC class Ia proteins. This peptide is referred to as Qdm. In this study, we report the isolation and sequencing of a heat shock protein 60-derived peptide (GMKFDRGYI) from Qa-1. This peptide is the dominant peptide bound to Qa-1 in the absence of Qdm. A Qa-1-restricted CTL clone recognizes this heat shock protein 60 peptide, further verifying that it binds to Qa-1 and a peptide from the homologous Salmonella typhimurium protein GroEL (GMQFDRGYL). These observations have implications for how Qa-1 can influence NK cell and T cell effector function via the TCR and CD94/NKG2 family members, and how this effect can change under conditions that cause the peptides bound to Qa-1 to change.

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“…The homoarginine method, during which a conversion of reactive lysine to homoarginine occurs, is possible to use for determination of reactive lysine (Kimmel, 1967). Within the guanidination reaction, lysine which is not linked to sugars is converted to the homoarginine before the sample is subjected to acid hydrolysis of protein (Kimmel, 1967).…”

Section: Homoarginine Methodsmentioning

confidence: 99%

“…Within the guanidination reaction, lysine which is not linked to sugars is converted to the homoarginine before the sample is subjected to acid hydrolysis of protein (Kimmel, 1967). When homoarginine method is used the content of reactive lysine is determined based on the analyzed amount of homoarginine which is formed during the guanidination reaction.…”

Section: Homoarginine Methodsmentioning

confidence: 99%

Methods for Determination Reactive Lysine in Heat-Treated Foods and Feeds

Brestenský¹,

Nitrayová²,

Heger³

et al. 2014

J microb biotech food sci

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Lysine is an essential amino acid, which is limited in foods of plant origin, especially in cereals. The heat-treatment of products containing proteins and reducing sugars results in formation of Maillard reactions during which the cross-linkages among epsilon amino groups (ε-NH2) and reducing sugars are created. Thus the protein-carbohydrate complex is formed. This complex contains an unreactive (unavailable) lysine, which is bound to reducing sugars and is not available in body. Hereby, the nutritive value of feeds and foods decreases. When a standard analytical method for analyses of amino acids is used, in products containing protein-carbohydrate complexes, it is not possible to analyze the content of reactive (available) and unreactive (unavailable) lysine, but only the content of total lysine. Therefore, when the standard amino acid analysis is used, the content of lysine in heat-treated feeds and foods is overestimated. In order to avoid this, some methods for determination of reactive lysine were developed. Among the best known, the homoarginine and furosine methods are included. Using these methods, in evaluation of nutritive value of feeds and foods, is of great importance because they allow to determine the extent of proteins, which were damaged during the heat treatment and thus we obtain information on objective nutritional protein quality of the product.

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[70] Guanidination of proteins

Cited by 101 publications

References 13 publications

Role of the alpha-amino group of protein in ubiquitin-mediated protein breakdown.

Role of the alpha-amino group of protein in ubiquitin-mediated protein breakdown.

A Peptide from Heat Shock Protein 60 Is the Dominant Peptide Bound To Qa-1 in the Absence of the MHC Class Ia Leader Sequence Peptide Qdm

Methods for Determination Reactive Lysine in Heat-Treated Foods and Feeds

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