Catalyzes the NADPH-dependent reduction of 7-cyano-7-deazaguanine (preQ0) to 7-aminomethyl-7-deazaguanine (preQ1). 7-aminomethyl-7-carbaguanine + 2 NADP(+) = 7-cyano-7-deazaguanine + 3 H(+) + 2 NADPH tRNA modification; tRNA-queuosine biosynthesis. Belongs to the GTP cyclohydrolase I family. QueF type 1 subfamily.