Origins
No ubiquitin and ubiquitination machinery are known to exist in prokaryotes. However, ubiquitin is believed to have descended from prokaryotic proteins similar to ThiS or MoaD. These prokaryotic proteins, despite having little sequence identity (ThiS has 14% identity to ubiquitin), share the same protein fold. These proteins also share sulfur chemistry with ubiquitin. MoaD, which is involved in molybdenum cofactor biosynthesis, interacts with MoeB, which acts like an E1 ubiquitin-activating enzyme for MoaD, strengthening the link between these prokaryotic proteins and the ubiquitin system. A similar system exists for ThiS, with its E1-like enzyme ThiF. It is also believed that the Saccharomyces cerevisiae protein Urm-1, a ubiquitin-related modifier, is a "molecular fossil" that connects the evolutionary relation with the prokaryotic ubiquitin-like molecules and ubiquitin.
Read more about this topic: Ubiquitin
Famous quotes containing the word origins:
“The origins of clothing are not practical. They are mystical and erotic. The primitive man in the wolf-pelt was not keeping dry; he was saying: “Look what I killed. Aren’t I the best?””
—Katharine Hamnett (b. 1948)
“The settlement of America had its origins in the unsettlement of Europe. America came into existence when the European was already so distant from the ancient ideas and ways of his birthplace that the whole span of the Atlantic did not widen the gulf.”
—Lewis Mumford (1895–1990)
“Compare the history of the novel to that of rock ‘n’ roll. Both started out a minority taste, became a mass taste, and then splintered into several subgenres. Both have been the typical cultural expressions of classes and epochs. Both started out aggressively fighting for their share of attention, novels attacking the drama, the tract, and the poem, rock attacking jazz and pop and rolling over classical music.”
—W. T. Lhamon, U.S. educator, critic. “Material Differences,” Deliberate Speed: The Origins of a Cultural Style in the American 1950s, Smithsonian (1990)