Microprotein
A microprotein (miP) is a small protein encoded from small open reading frame (smORF). [1] They are a class of protein with a single protein domain that are related to multidomain proteins. [2] Microproteins regulate larger multidomain proteins at the post-translational level. [3] Microproteins are analogous to microRNAs (miRNAs) and heterodimerize with their targets causing dominant and negative effects (Eguen). [4] In animals and plants, microproteins have been found to greatly influence the biological processes. [2] Because of microproteins dominant effects on their targets, microproteins are currently being studied for potential applications in biotechnology. [2]
History
The first microprotein (miP) discovered was during a research in the early 1990s on genes for basic helix–loop–helix (bHLH) transcription factors from a murine erythroleukaemia cell cDNA library. [3] The protein was found to be an inhibitor of DNA binding (Id), and it negatively regulate transcription factor complex. [3] The Id protein was 16 kDa and consisted of a helix-loop-helix (HLH) domain. [2] The microprotein formed bHLH/HLH heterodimers which disrupted the functional basic helix–loop–helix (bHLH) homodimers. [2] The first microprotein discovered in plants was the LITTLE ZIPPER (ZPR) protein. [2] The LTTLE ZIPPPER protein contains a leucine zipper domain but does not have the domains required for DNA binding and transcription activation. [2] Thus, LITTLE ZIPPER protein is analogous to the Id protein. [2] Despite not all proteins being small, in 2011, this class of protein was given the named microproteins because their negative regulatory actions are similar to those of miRNAs. [3]
Evolutionary, the Id protein or proteins similar to Id are found in all animals. [3] In plants, microproteins are only found in higher order. [3] However, the homeodomain transcription factors that belong to the three-amino-acid loop-extension (TALE) family are targets of microproteins, and this homeodomain proteins are conserved in animals, plants, and fungi. [3]
Structure
Microproteins are generally small proteins with a single protein domain. [2] [4] The active form of microproteins are translated from smORF. [1] The smORF codons which microproteins are translated from can be less than 100 codons. [1] However, not all microproteins are small, and the name was given because their actions are analogous to miRNAs. [3]
Function
The function of microproteins is post-translational regulators. [3] Microproteins disrupt the formation of heterodimeric, homodimeric, or multimeric complexes. [4] Furthermore, microproteins can interact with any protein that require functional dimers to function normally. [3] The primary targets of microproteins are transcription factors that bind to DNA as dimers. [3] Microproteins regulate these complexes by creating homotypic dimers with the targets and inhibit protein complex function. [3] There are two types of miP inhibitions: homotypic miP inhibition and heterotypic miP inhibition. [4] In homotypic miP inhibition, microproteins interact with proteins with similar protein-protein interaction (PPI) domain. [4] In heterotypic miP inhibition, microproteins interact with proteins with different but compatible PPI domain. [4] In both types of inhibition, microproteins interfere and prevent the PPI domains from interacting with their normal proteins. [4]
References
- ↑ 1.0 1.1 1.2 "The Dark Matter of the Human Proteome" (in en). https://www.the-scientist.com/features/the-dark-matter-of-the-human-proteome-65628.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Bhati, Kaushal Kumar; Blaakmeer, Anko; Paredes, Esther Botterweg; Dolde, Ulla; Eguen, Tenai; Hong, Shin-Young; Rodrigues, Vandasue; Straub, Daniel; et al. (2018-04-18). "Approaches to identify and characterize microProteins and their potential uses in biotechnology". Cellular and Molecular Life Sciences 75 (14): 2529–2536. doi:. ISSN 1420-682X. http://dx.doi.org/10.1007/s00018-018-2818-8.
- ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 Staudt, Annica-Carolin; Wenkel, Stephan (2010-12-10). "Regulation of protein function by ‘microProteins’". EMBO reports 12 (1): 35–42. doi:. ISSN 1469-221X. http://dx.doi.org/10.1038/embor.2010.196.
- ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 Eguen, T; Straub, D; Graeff, M; Wenkel, S (August 2015). "MicroProteins: small size-big impact". Trends in Plant Science 20 (8). doi:.
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