The gene encompasses 105 kb; it has 18 exons.

The MELK gene generates multiple variants (potentially 28 different mRNAs). The longest mRNA is composed of 3218 nucleotides.

MELK (Maternal Embryonic Leucine zipper Kinase) belongs to the CAMK serine/threonine protein kinase superfamily. Melk is a protein serine/threonine kinase that is maximally active during mitosis. It is involved in diverse functions such as cell cycle, cytokinesis, mRNA splicing and apoptosis.

The full-length protein is 651 amino acids with an estimated molecular weight of approximately 74,5 kDa.

MELK is expressed in cells of various tissue origins. MELK is highly expressed in oocytes, spermatogonia and embryos, which is indicative of a role in the germ-cell development. MELK is highly expressed in a large panel of cancers MELK expression is dependant on cell transformation (Gray et al., 2005). Its expression is strongly dependant on cell-cycle: MELK is undetectable in cells which have exited cell cycle (Badouel et al., 2010).

Cytoplasm, nucleus and cell cortex.

The exact function of MELK is currently unknown, however MELK was shown to be involved in cell cycle progression via the protein phosphatase CDC25B phosphorylation (Blot et al., 2002), in cytokinesis (Le Page et al., 2011), in apoptosis via its interaction with the Bcl-2 family of proapoptotic genes (Lin et al., 2007) and apoptosis signal-regulating kinase (ASK1) (Jung et al., 2008) and in inhibition of mRNA splicing during mitosis via its association with NIPP1 (Vulsteke et al., 2004). MELK function is required for mammary tumorigenesis in vivo (Hebbard et al., 2010).

MELK belongs to the Kin1/PAR-1/MARK family of protein kinases found from yeast to human. These kinases are involved in cell polarity, dynamics of microtubules and intracellular signalisation.