Open AccessProtein A Isolated from Staphylococcus aureus after Digestion with Lysostaphin
Author(s) -
Sjöquist John,
Meloun Bedrich,
Hjelm Hans
Publication year - 1972
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1972.tb02023.x
Subject(s) - lysostaphin , amino acid , biochemistry , protein a/g , protein subunit , peptidoglycan , lysozyme , staphylococcus aureus , chromatography , chemistry , lysine , protein a , biology , bacteria , enzyme , fusion protein , recombinant dna , gene , antibody , immunology , genetics
Previous methods which have been used for the preparation of protein A, such as thermal release of protein A with lysozyme from the bacteria, have given a heterogenous product in a low yield. The present publication reports the isolation procedure of protein A from Staphylococcus aureus digested by lysostaphin for 2 h at 37°C. 450—500 mg of protein A was obtained from 300 g of wet bacteria. The preparation is homogenous as seen from its disc electrophoretic pattern. Amino acid composition was determined and based on a molecular weight of 42000. The number of amino acid residues found was 378 ± 6. Less than 0.2% hexosamines was present. The ultraviolet spectrum and the absorption coefficient, A 1% 275nm = 1.65 of protein A is given. Less than 0.1 mol amino terminal amino acid per mol protein was detected which indicates that the protein has a blocked N‐terminal amino acid. The protein was slowly digested with a mixture of carboxypeptidase A and B and 2 mol lysine/mol protein was released. Precipitation of protein A with normal human γ‐globulin gave an IgG: protein A molar ratio of 2.1:1 within the equivalence zone. The results are discussed with regard to the subunit structure of the protein and the type of attachment of protein A to the peptidoglycan part of the cell wall.