抄録
Amino acid propensity in the central and the end regions of transmembrane helices was compared to that in the loop region, using the data of membrane proteins whose 3D-structure is already known. Polar residues showed characteristic distribution in transmembrane helical regions, depending on the type of amino acids. The polar residues with large side chains (Lys, Arg, His, Glu and Gln) were located in the end region more than the small polar residues (Asp, Asn), suggesting that the side chains having the detergent-like characteristics stabilize the end of transmembrane helices. The positively charged residues were more preferable in the inside end region than in the outside. However, this tendency was significant for the proteins in the inner membrane of mitochondria from mitochondrial DNA, in contrast to the symmetrical distribution of the large polar residues for the membrane proteins from genomic DNA. The physical factors for the determination of membrane protein topology was discussed on the position dependent propensity.
