Methionine cyanogen bromide cleavage

Cyanogen bromide cleavage of the polypeptide subunit should yield 4 peptides if the subunit contains 3 methionines (Table III). Cleavage products were isolated by gel filtration through Sephadex G-75 columns and analyzed for purity with polyacrylamide gel electrophoresis in 8 M urea containing 0.1 M thioglycolate. Four peptide products were obtained (34). 

Figure 5-3. Mechanism of cyanogen bromide cleavage. Cyanogen bromide cleaves peptide chains at methionine residues. The reagent attacks the sulphur atom, and methylisothio-cyanate is cleaved from the resulting adduct,...

It is not apparent whether the differences in the sequence of HSA reported by the two groups were the outcome of microheterogeneity, which was often demonstrated, or whether they were due to experimental errors. At the moment, the only strong evidence for microheterogeneity of albumin as a result of the primary structure comes from the work by Lapresle and Doyen (1975), who showed, by cyanogen bromide cleavage of HSA, that about 16% of the molecules lacked methionine at position 123. 

The use of BNPS-skatole for the selective cleavage of the tryptophanyl peptide bond has been proved useful in sequence studies. The cleavage yields so far obtained (about 50-70%) with peptides (289, 371) and proteins (119) indicate that the reagent is the best so far available for the cleavage of the tryptophanyl peptide bond and approaches in utility the cyanogen bromide cleavage of methionine peptide bonds (375). The reagent has been successfully applied to staphylococcal nuclease... 

The most commonly utilized chemical cleavage agent is cyanogen bromide (it cleaves the peptide bond on the carboxyl side of methionine residues). V8 protease, produced by certain staphylococci, along with trypsin are two of the more commonly used proteolytic-based fragmentation agents. 

In the treatment of RNase-A with cyanogen bromide, chain cleavage occurs at Met 13. The peptide comprising residues 1-13, where 13 is now homoserine or homoserine lactone rather than methionine, is designated C-peptide (139). This derivative added to S-protein at a molar ratio of 600 1 gave between 50 and 80% of the maximum activity. 

The cleavage of polypeptide chains at methionine residues by cyanogen bromide. The cleavage reaction is accompanied by the conversion of the newly formed free carboxyl-terminal methionine to homoserine lactone. 

Figure 1 Strategy for cloning a peptide-coding sequence (CDS) as tandem repeats in the vector pET31b. The resulting fusion protein, comprising the ketosteroid isomerase (KSI), peptide repeats, and His-tag, is targeted to inclusion bodies. The fusion protein can be recovered and cleaved, in this case, with cyanogen bromide (CNBr) which acts at the methionine (M) residues allowing further separation of pure peptide from the other fusion components. The cleavage by CNBr results in a C-terminal homoserine lactone (hsl) on each peptide monomer.

A nonenzymatic. chemical method for specific cleavage of polypeptides involves the reaction of cyanogen bromide, CNBr, with methionine residues ... 

Figure 8 28. Reaction of cyanogen bromide with methionine residues, followed by cleavage of the peptide chain containing those residues. [From E. Cross, in Methods of Enzymology, Vol. II (C. H. W. Heis, Ed.), Academic Press, New York, 1967, p. 238.]...

A marked improvement in the cleavage of methionine peptides was achieved by the use of cyanogen bromide (Gross and Witkop, 1961). Pro-... 

The new selective cleavage of methionine peptide bonds with cyanogen bromide offers more promise of success. There are about twenty methionine residues in 7-globulin and three to four methionines in the 50,000 molecular-weight fraction which has retained the power to bind antigen (Porter, 1957). 

A study of the reaction of cyanogen bromide in 0.3 N HCl with the common amino acids showed that, besides methionine, only cysteine (cf. Swan, 1958), but neither cystine, tyrosine, nor tryptophan, reacted. Cleavage of... 

Specific cleavage can be achieved by chemical or enzymatic methods. For example, cyanogen bromide (CNBr) splits polypeptide chains only on the carboxyl side of methionine residues (Figure 4.23). 

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