Are non-functional, unfolded proteins ('junk proteins') common in the genome?
It has recently been shown that many proteins are unfolded in their functional state. In addition, a large number of stretches of protein sequences are predicted to be unfolded. It has been argued that the high frequency of occurrence of these predicted unfolded sequences indicates that the majority of these sequences must also be functional. These sequences tend to be of low complexity. It is well established that certain types of low-complexity sequences are genetically unstable, and are prone to expand in the genome. It is possible, therefore, that in addition to these well-characterised functional unfolded proteins, there are a large number of unfolded proteins that are non-functional. Analogous to 'junk DNA' these protein sequences may arise due to physical characteristics of DNA. Their high frequency may reflect, therefore, the high probability of expansion in the genome. Such 'junk proteins' would not be advantageous, and may be mildly deleterious to the cell.
Lovell
Simon C
SC
School of Biological Science, University of Manchester, 2.205 Stopford Building, Oxford Rd, Manchester M13 9PT, UK. simon.lovell@man.ac.uk
D000595:Amino Acid Sequence; D016678:Genome; D042822:Genomic Instability; D017510:Protein Folding; D011506:Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D013329:Structure-Activity Relationship
D011506:Proteins