**4. Interaction of optineurin with cellular proteins**

Optineurin is predominantly a coiled coil protein of 577 amino acids [27] (Figure 1). It has a well defined ubiquitin-binding UBAN domain (UBD) [28], and a zinc finger domain, which is also believed to bind to ubiquitin [29]. Optineurin interacts with a diverse array of cellular proteins through multiple interaction domains [28, 30-45] (Figure 1C). Over 20 proteins are known to interact with optineurin but functional significance of only some of these interactions is known. Emerging evidences suggest that optineurin is an adaptor protein with no known enzymatic or catalytic activity. Therefore, its functions are likely to be mediated by interaction with other proteins [46, 47].
