Structure and Antigenicity of Hen Egg-White Lysozyme Fragments.

Purification of a lysozyme-digest resulted in the isolation of two main regions of the molecule, namely sequence (57-107) denoted loop fragment (see the accompanying paper), and sequence (1-27) linked to sequence (122-129) through disulfide bridge I-VIII (Jolles et al., 1963), denoted NC-peptide. Inhibition of lysozyme-anti-lysozyme precipitation showed that NC-peptide reacted with about 10% of all goat anti-lysozyme antibodies. It was suggested that these antibodies react with a conformation-dependent determinant including tyrosine 20 and 30. In water or in aqueous salt solution, NC-fragment retained about 20% of its "native" alpha-helical amount (i.e. the amount of helicity this fragment possesses when integrated in the lysozyme-molecule). Reduction and alkylation of the I-VIII disulfide bridge abolished most of the spatial conformation, as was obvious from the circular dichroism curve isolated N-peptide. Long-range interactions between the N and C terminal parts of the molecule, therefore, seem to stabilize the native lysozyme molecule. [ABSTRACT FROM AUTHOR]