tokens: These include the genes , undefined 1 ( UD1 ) , UD2 , and UD3 , each coding for proteins of unknown function , the ken gene encoding a new Kruppel - like putative transcription factor , the fly homologues of the mammalian mitochondrial trifunctional enzyme ( thiolase ) , and the TAR DNA - binding protein - 43 ( TBPH ) , the first nonvertebrate member of the transmembrane 4 superfamily ( TM4SF ) gene , a new homeodomain gene , and a gene coding for a putative nuclear binding protein ( PNBP ) that is homologous to maleless , and a Copia - like element .