In biochemistry, a protein trimer is a Macromolecule complex formed by three, usually covalent bond, like or . A protein trimer often occurs from the assembly of a protein's quaternary structure.
A homotrimer would be formed by three identical .
Porins usually arrange themselves in membranes as trimers.
Bacteriophage T4 tail fiber
Multiple copies of a polypeptide encoded by a
gene often can form an aggregate referred to as a multimer.
[Crick FH, Orgel LE. The theory of inter-allelic complementation. J Mol Biol. 1964 Jan;8:161-5. . ] When a multimer is formed from polypeptides produced by two different
mutant of a particular gene, the mixed multimer may exhibit greater functional activity than the unmixed multimers formed by each of the mutants alone. When a mixed multimer displays increased functionality relative to the unmixed multimers, the phenomenon is referred to as intragenic complementation. The distal portion of each of the bacteriophage T4 tail fibers is encoded by gene
37 and mutants defective in this gene undergo intragenic complementation.
[Bernstein H, Edgar RS, Denhardt GH. Intragenic complementation among temperature sensitive mutants of bacteriophage T4D. Genetics. 1965;51(6):987-1002.] This finding indicated that the distal tail fibers are a multimer of the gene
37 encoded polypeptide. An analysis of the complementation data further indicated that the polypeptides making up the multimer were folded back on themselves in the form of a hairpin. A further high-resolution crystal structure analysis of the distal tail fiber indicated that the gene
37 polypeptides are present as a trimer and that each polypeptide of the trimer is folded back on itself in a hairpin configuration.
[Bartual SG, Otero JM, Garcia-Doval C, et al. Structure of the bacteriophage T4 long tail fiber receptor-binding tip. Proc Natl Acad Sci U S A. 2010;107(47):20287-20292. ]
See also
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Spike protein (coronavirus)
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Hemagglutinin (influenza)
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Oligomer
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Protein quaternary structure
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Trimer (chemistry)
