Slit refers to a secreted protein that is most widely known as a repulsive axon guidance cue, and Robo refers to its transmembrane protein receptor. There are four different Robos and three Slits in vertebrates: Robo1, Robo2, Robo3/Rig-1, and Robo4, and Slit1, Slit2, Slit3.[1] There are three Robos and a single Slit in Drosophila. The corresponding Slit and Robo homologues in C. elegans are Slt and Sax-3, respectively.[2]
Slits are characterized by four distinct domains, each containing variable numbers of leucine-rich repeats (LRRs),[3] seven to nine EGF repeats,[4][5] an ALPS domain (Agrin, Perlecan, Laminin, Slit), and a cysteine knot.[6] Robos are characterized by five Ig-like domains, three fibronectin type III (FNIII) repeats, a transmembrane portion, and an intracellular tail with up to four conserved cytoplasmic motifs: CC0 (a potential site of tyrosinephosphorylation),[7] CC1 (also a potential site of tyrosine phosphorylation and binds P3 domain of netrin-1 receptor DCC),[8] CC2 (polyproline stretch; consensus binding site for Ena/Vasp proteins),[7] and CC3 (polyproline stretch).[9]
^Rothberg JM, Hartley DA, Walther Z, Artavanis-Tsakonas S (December 1988). "slit: an EGF-homologous locus of D. melanogaster involved in the development of the embryonic central nervous system". Cell. 55 (6): 1047–59. doi:10.1016/0092-8674(88)90249-8. PMID3144436. S2CID9325118.