ubiquitin

Ubiquitin is a small (8.5 kDa) regulatory protein that has been found in almost all tissues () of eukaryotic organisms. It was discovered in 1975 by Gideon Goldstein and further characterized throughout the 1970s and 1980s. There are four genes in the human genome that produce ubiquitin: UBB, UBC,  UBA52 and RPS27A.