title: Families of proteins forming transmembrane channels.
abstract: Channel-forming proteins/peptides fall into over 100 currently recognized families, most of which are restricted to prokaryotes or eukaryotes, but a few of which are ubiquitous. These proteins fall into three major currently recognized classes: (i) alpha-helix-type channels present in bacterial, archaeal and eukaryotic cytoplasmic and organellar membranes, (ii) beta-barrel-type porins present in the outer membranes of Gram-negative bacterial cells, mitochondria and chloroplasts, and (iii) protein/peptide toxins targeted to the cytoplasmic membranes of cells other than those that synthesize the toxins. High-resolution 3-dimensional structural data are available for representative proteins/peptides of all three of these channel-forming types. Each type exhibits distinctive features that distinguish them from the other channel protein types and from carriers. Structural, functional, and evolutionary aspects of transmembrane channel-formers are discussed.
authors.affiliation: Department of Biology, University of California at San Diego, La Jolla, CA 92093-0116, USA.
authors.forename: M H
authors.initials: MH
authors.lastname: Saier
mesh_terms: D001426:Bacterial Proteins; D001694:Biological Warfare; D002352:Carrier Proteins / Q000145:classification* / Q000502:physiology; D019143:Evolution, Molecular; D006801:Humans; D007473:Ion Channels / Q000145:classification* / Q000502:physiology; D009238:N-Acetylmuramoyl-L-alanine Amidase; D018272:Porins / Q000145:classification / Q000502:physiology; D014118:Toxins, Biological / Q000145:classification
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D007473:Ion Channels; D018272:Porins; D014118:Toxins, Biological; C108616:LytH protein, Staphylococcus aureus; D009238:N-Acetylmuramoyl-L-alanine Amidase