This domain is found in Maternal embryonic leucine zipper kinase from humans (MELK) and similar proteins from animals. MELK is a member of the snf1/AMPK family of serine-threonine kinases that has been associated with various cellular processes, including stem cell renewal, cell cycle progression, and pre-mRNA splicing. It is upregulated in several types of tumour. MELK is organised into three domains: an N-terminal kinase domain (Pfam:PF00069), a ubiquitin associated (UBA) domain (this entry) and a C-terminal kinase associated domain (KA1, Pfam:PF02149). This domain adopts a compact configuration consisting of three alpha-helices organised in a "U"-shaped fold, with the first helix antiparallel to the third one [1-5].

1: Conformational instability of the MARK3 UBA domain compromises ubiquitin recognition and promotes interaction with the adjacent kinase domain. Murphy JM, Korzhnev DM, Ceccarelli DF, Briant DJ, Zarrine-Afsar A, Sicheri F, Kay LE, Pawson T; Proc Natl Acad Sci U S A. 2007;104:14336-14341. PMID:17726107

2: The structures of the kinase domain and UBA domain of MPK38 suggest the activation mechanism for kinase activity. Cho YS, Yoo J, Park S, Cho HS; Acta Crystallogr D Biol Crystallogr. 2014;70:514-521. PMID:24531485

3: Structural insight into maternal embryonic leucine zipper kinase (MELK) conformation and inhibition toward structure-based drug design. Canevari G, Re Depaolini S, Cucchi U, Bertrand JA, Casale E, Perrera C, Forte B, Carpinelli P, Felder ER; Biochemistry. 2013;52:6380-6387. PMID:23914841

4: The crystal structure of MPK38 in complex with OTSSP167, an orally administrative MELK selective inhibitor. Cho YS, Kang Y, Kim K, Cha YJ, Cho HS; Biochem Biophys Res Commun. 2014;447:7-11. PMID:24657156

5: Fragment-based discovery of type I inhibitors of maternal embryonic leucine zipper kinase. Johnson CN, Berdini V, Beke L, Bonnet P, Brehmer D, Coyle JE, Day PJ, Frederickson M, Freyne EJ, Gilissen RA, Hamlett CC, Howard S, Meerpoel L, McMenamin R, Patel S, Rees DC, Sharff A, Sommen F, Wu T, Linders JT; ACS Med Chem Lett. 2014;6:25-30. PMID:25589925