Abstract
Prion proteins were initially associated with diseases such as Creutzfeldt Jakob and transmissible spongiform encephalopathies. However, deeper research revealed them as versatile tools, exploited by the cells to execute fascinating functions, acting as epigenetic elements or building membrane free compartments in eukaryotes. One of the most intriguing properties of prion proteins is their ability to propagate a conformational assembly, even across species. In this context, it has been observed that bacterial amyloids can trigger the formation of protein aggregates by interacting with host proteins. As our life is closely linked to bacteria, either through a parasitic or symbiotic relationship, prion-like proteins produced by bacterial cells might play a role in this association. Bioinformatics is helping us to understand the factors that determine conformational conversion and infectivity in prion-like proteins. We have used PrionScan to detect prion domains in 839 different bacteria proteomes, detecting 2200 putative prions in these organisms. We studied this set of proteins in order to try to understand their functional role and structural properties. Our results suggest that these bacterial polypeptides are associated to peripheral rearrangement, macromolecular assembly, cell adaptability, and invasion. Overall, these data could reveal new threats and therapeutic targets associated to infectious diseases.
Highlights
An increasing number of human diseases are being associated with amyloid forming proteins
We have analyzed 839 Bacteria proteomes containing a total of 860337 proteins with PrionScan, from which we detected 2200 putative prion proteins scoring higher than 50 bits in the algorithm scale (Espinosa Angarica et al, 2013) accounting for a 0.3% of the complete protein dataset
Because the formation of amyloids comes at expenses of the formation of transient toxic species cells tightly control the assembly of these macromolecular structures and how they can interact with proteins from other species (Zhou et al, 2012; Schwartz and Boles, 2013; Evans et al, 2015; Taylor and Matthews, 2015)
Summary
An increasing number of human diseases are being associated with amyloid forming proteins. Classical amyloid proteins contain specific regions rich in hydrophobic residues that lead the protein self-assembly, prion-like proteins exhibit domains that are commonly enriched in asparagine and glutamine (Q/N) (Dorsman et al, 2002; Fändrich and Dobson, 2002; Halfmann et al, 2011) and in glycine, serine and tyrosine residues (Kato et al, 2012) This pattern has been found in human proteins associated to neurodegenerative diseases, such as FUS (dementia) or TDP43 (amyotrophic lateral sclerosis; Kato et al, 2012). It has been found that the propagation of amyloid aggregation depends on characteristics such as the degree of over/under representation of specific residues and the length of the considered low complexity region (Ross et al, 2004, 2005; Toombs et al, 2010)
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