[Protein motifs and their structure-functional role]

The review deals with repeating fragments of amino acid sequences, so-called "motifs", that are important in maintaining structural integrity and/or function of various proteins, especially those interacting with phospholipid aggregates. The occurrence of Phe-Leu-Gly motif characteristic for the amino acid sequence of the primate immuno-deficiency viruses fusion peptides is analysed in various proteins, as well as tripeptide fragments of general formula Xaa-Xah-Gly (Xaa-Phe, Tyr; Xab-hydrophobic amino acids Ala, Val, Leu, Ile) homologous to the above motif and retro-sequences Gly-Xab-Xaa. These tripeptide repeats are characteristic for the amino acid sequences of complex membrane proteins, viral envelope proteins, proteinases and proteins connected with energy transfer or interacting with lipids. These repeats are frequently met in conservative regions of amino acid sequences, in sites readily accessible for other molecules at the boundary of or between structured fragments, this being due to the backbone semi-coiled form's preference in the given amino acid fragment. This protein motif appears to play an important role at the initial stages of the large protein's interaction with the phospholipid membrane.