sentence: Precise structural analyses will be needed to understand the implications of the context of the tandem GA pairs on the functional activity of the SECIS.Although SBP2 has been proposed to dictate the expression of the selenoproteome , the affinity of SBP2 for the Gpx3 and SelX SECIS elements differed by only 2-fold despite their 350-fold difference in directing UGA recoding in transfected cells .