title: How important are transmembrane helices of bitopic membrane proteins?
abstract: The topology of a bitopic membrane protein consists of a single transmembrane helix connecting two extra-membranous domains. As opposed to helices from polytopic proteins, the transmembrane helices of bitopic proteins were initially considered as merely hydrophobic anchors, while more recent studies have begun to shed light on their role in the protein's function. Herein the overall importance of transmembrane helices from bitopic membrane proteins was analyzed using a relative conservation analysis. Interestingly, the transmembrane domains of bitopic proteins are on average, significantly more conserved than the remainder of the protein, even when taking into account their smaller amino acid repertoire. Analysis of highly conserved transmembrane domains did not reveal any unifying consensus, pointing to a great diversity in their conservation patterns. However, Fourier power spectrum analysis was able to show that regardless of the conservation motif, in most sequences a significant conservation moment was observed, in that one side of the helix was conserved while the other was not. Taken together, it may be possible to conclude that a significant proportion of transmembrane helices from bitopic membrane proteins participate in specific interactions, in a variety of modes in the plane of the lipid bilayer.
authors.affiliation: The Alexander Silberman Institute of Life Sciences, Department of Biological Chemistry, The Hebrew University, Edmund J. Safra Campus, Givat-Ram, Jerusalem 91904, Israel.
authors.forename: Moti
authors.initials: M
authors.lastname: Zviling
authors.forename: Uzi
authors.initials: U
authors.lastname: Kochva
authors.forename: Isaiah T
authors.initials: IT
authors.lastname: Arkin
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000596:Amino Acids; D016384:Consensus Sequence; D030562:Databases, Protein; D019143:Evolution, Molecular; D005583:Fourier Analysis; D057927:Hydrophobic and Hydrophilic Interactions; D008051:Lipid Bilayers; D008565:Membrane Proteins / Q000737:chemistry*; D008958:Models, Molecular; D010802:Phylogeny; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid
chemical_list: D000596:Amino Acids; D008051:Lipid Bilayers; D008565:Membrane Proteins