Sequence of the murein-lipoprotein and the attachment site of the lipid.

Abstract

The primary structure of a covalent lipoglycoprotein (murein · lipoprotein) from the cell wall of Escherichia coli is presented. The amino acid sequence consists of 57 residues. The lipid is attached to the N‐terminal serine and the murein is bound to the 6‐amino group of the C‐terminal lysine of the lipoprotein. The repetitive design of the sequence suggests a very conservative evolution in which a structural gene coding for 15 amino acids was duplicated once and then only half of this gene, thus coding for 7 amino acids was fused four times with the first 29 amino acids. Some deletions but only few exchanges of amino acids apparently occurred.This structural membrane lipoprotein aggregates strongly when released from the murein by lysozyme digestion. The molecular weight was therefore determined in 2%, 0.5% and 0.1% dodecylsulfate by polyacrylamide gel electrophoresis and gel chromatography. The molecular weight of 13000 thus found deviated from that of 10000 calculated from the sum of the amino acids, the lipid as known so far and the part of the murein remaining bound to the lipoprotein. This was not due to a different amount of dodecylsulfate binding by the lipoprotein compared with proteins containing no lipid but may be due to a more spherical shape of the small molecule in contrast to the rod‐like shape of standard proteins in dodecylsulfate.