Tail-anchored membrane proteins (TAMPs) are unusual integral membrane proteins, because they are obliged to target to membranes post-translationally. Although predicted to comprise 3-5% of all transmembrane proteins, only a small number of TAMPs are well characterized. To identify novel putative TAMPs across different species, we used TAMPfinder software to identify 859, 657 and 119 putative TAMPs in human (Homo sapiens), plant (Arabidopsis thaliana), and yeast (Saccharomyces cerevisiae), respectively. We validated a subset of previously uncharacterized human and plant TAMP proteins by expressing them in cells and visualizing them at subcellular membranes by fluorescence microscopy. We also analyzed them by carbonate extraction to determine if they are integral membrane proteins or by bimolecular fluorescence complementation to determine the membrane topology of the predicted plant TAMPs. With the exception of the pro-apoptotic protein harakiri, which is, peripherally rather than integrally, bound to the membrane this subset of novel proteins behaved like genuine TAMPs.
Comprehensive bioinformatics analysis revealed previously unappreciated common and species-specific features such as the unusual size distribution of and the propensity of TAMP proteins to be part of larger complexes. Novel features of the amino-acid sequences that anchor TAMPs to membranes were also revealed. The lists of TAMPs and annotations can be accessed using the links at the right of the page.
The application used to predict TAMPs was created by CRC Systems, with additional technical support from Group ICP. Information and documentation is available here.
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