Amino-acid composition of the covalent rigid-layer lipoprotein in cell walls of Proteus mirabilis.

Cell walls of Proteus mirabilis in the stationary phase of growth contain a lipoprotein in covalent linkage to peptidoglycan and probably also in free form in the outer membrane. The protein moiety of this lipoprotein is composed of about 50 amino acids and has an approximate molecular weight of 5500. The Proteus lipoprotein has glycine and phenylalanine as specific components which are not present in lipoproteins of other enteric bacteria. Treatment of the peptidoglycan-lipoprotein complex of Proteus with trypsin leaves lysine as the only lipoprotein amino acid attached to the peptidoglycan. This suggests that in P. mirabilis, as in Escherichia coli, the lipoprotein is linked to the peptidoglycan by its C-terminal lysine residue.