the ski2 like helicase mtr4p was discovered during the screening of heat resistant mutants that gather poly(a) rna in the nucleus and is mainly involved in unwinding activity. mtr4p (also called as dob1p) is an sf2 helicase and belongs to dexh-box rna helicases family consisting of two reca like domains. it also consists of wh domain (winged helix domain), an arch domain (also called as stalk and kow domain [kyprides, ouzounis, woese domain]) and helical bundle domain. the packing of the wh and helical bundle domains on surface of the helicase core results in the formation of a channel for ssrna.