Ubiquitin can be covalently bound to an internal lysine of a target protein. This process is mediated by a complex and highly selective enzymatic machinery.
Ubiquitin conjugates take the form of one or more multimeric chains.
Faf is required to regulate the number of photoreceptors during eye development . Mutants lacking zygotic faf function develop to adulthood, but have rough eyes caused by the presence of one to two ectopic outer photoreceptors per ommatidium. The role of deubiquitination enzymes in the ubiquitin pathway has best been characterized in Saccharomyces cerevisiae where 15 genes have been identified. The deubiquitination enzymes can broadly be divided into two groups, one promoting and the other inhibiting ubiquitin-dependent proteolysis. Sequence alignments indicate that Faf may be functionally homologous to Doa4, which promotes efficient ubiquitin-dependent degradation.