label: a 5'-end diphospho-(purine-ribonucleoside) in mRNA + GTP + H(+) <=> a 5'-end (5'-triphosphoguanosine)-(purine-ribonucleoside) in mRNA + diphosphate
label_lc: a 5'-end diphospho-(purine-ribonucleoside) in mrna + gtp + h(+) <=> a 5'-end (5'-triphosphoguanosine)-(purine-ribonucleoside) in mrna + diphosphate