Abstract
Soluble mucopeptide was prepared by lysozyme treatment of acid-extracted walls of B. licheniformis N.C.T.C. 6346 and separated into fractions differing in molecular size by chromatography on Sephadex G-25 and G-50. About 16% of the weight of soluble mucopeptide has a weight-average molecular weight in excess of 20 000. About 1/2 has a weight-average molecular weight of less than 2000, and the balance of soluble mucopeptide is of intermediate size. There is a correlation between the weight-average molecular weight, the number of non-reducing muramic acid residues and the proportion of diaminoplmelic acid residues recovered after treatment with l-fluoro-2,4-dinitrobenzene in the mucopeptide fractions isolated from Sephadex. The extent of cross-linking between peptide side chains is relatively low, even in mucopeptide material of the large molecular size. The small amount of residual P present in preparations of B. licheniformis soluble mucopeptide remains associated mainly with mucopeptide material of large molecular size. The mucopeptide components of lowest molecular weight not produced as artifacts during the preparation of soluble mucopeptide are apparently incorporated in the insoluble mucopeptide present in walls of exponentially growing cells. Soluble mucopeptide isolated in a complex with acidic polymers after lysozyme treatment of walls of B. licheniformis N.C.T.C. 6346 and Bacillus subtilis W23 retains a high molecular weight when the covalcnt bonds between mucopeptide and the acidic polymers are broken. Pure fragments were isolated from B. licheniformis soluble mucopeptide. A major component, C1, of the material of smallest size is made up of one residue each of N-acetylglucosamine, N-acetylmuramic acid, L-alanine, glutamic acid and diaminoplmelic acid. The N-acetylglucosamine is in [beta]-glycosidic linkage with a reducing N-acetylmuramic acid residue. The peptide unit is probably amidated. A quantitatively minor component, C2, has amino-acid and amino sugar composition identical with that of component Cl, but probably lacks an amide group. Another fragment, B1, is made up of 2 molecules of component Cl or C2 that are joined together through a molecule of D-alanine.

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