Comparing the efficiencies of various non-AUG initiator codons in GRS1. (A) Complementation assays for mitochondrial GlyRS activity. The grs1- strain was transformed with various GRS1 constructs, and the growth phenotypes of the transformants were tested. (B) Assay of initiating activities by Western blots. Upper panel, GlyRS-LexA fusion; lower panel, PGK (as loading controls). (C) Assay of the relative initiating activities by Western blots. Protein extracts prepared from the construct with an ATG initiator codon were 2-fold serially diluted and compared to those from constructs with non-ATG initiator codons. The quantitative data for the relative expression levels of these constructs are shown as a separate diagram at the bottom. (D) RT-PCR. Relative amounts of specific GRS1-lexA mRNAs generated from each construct were determined by RT-PCR. The GRS1 sequences used in the GRS1-lexA fusion constructs 1~11 in (B) were respectively transferred from constructs 1~11 shown in (A). In (C) and (D) the numbers 1~11 (circled) denote constructs shown in (B).