a 5'-end (5'-triphosphoguanosine)-adenosine in mRNA + diphosphate => a 5'-end diphospho-adenosine in mRNA + GTP + H(+)
a 5'-end (5'-triphosphoguanosine)-adenosine in mrna + diphosphate => a 5'-end diphospho-adenosine in mrna + gtp + h(+)