Poly(A) Polymerase, E. coli

What it means: Source Organism is where the enzyme gene comes from. E. coli poly(A) polymerase (E-PAP) behaves differently from the yeast enzyme, so the source is a functional distinction rather than a manufacturing detail.

Why it matters:

• E-PAP works sequence-independently, so it does not need a recognition site and tails almost any accessible 3′ end.
• That makes it the better choice for heterogeneous RNA populations where you cannot design around a consensus.
• The yeast enzyme is generally preferred for oligonucleotide labelling and for tailing long RNA templates.

How to interpret here: Choose E-PAP when the input is a mixed or unknown RNA pool — small RNA library preparation, 3′-end labelling, general RNA detection. For long defined templates, compare against the yeast enzyme (Cat. No. E017).

Tip: Because it tails almost anything with a free 3′-OH, degraded RNA in the sample is tailed too — check input integrity first.

What it means: Tailing Mechanism describes how the enzyme decides what to add. Template-independent means it adds adenosine residues without reading a template strand — the tail is synthesised, not copied.

Why it matters:

• No template is needed, so a poly(A) tail can be added to any RNA regardless of what it encodes.
• Tail length is governed by reaction time, enzyme and ATP concentration rather than by a sequence, so it must be controlled empirically.
• A synthetic poly(A) tail gives an oligo-dT priming site, which is what lets non-polyadenylated RNA enter standard mRNA workflows.

How to interpret here: Control tail length by shortening or lengthening the incubation rather than expecting a fixed product size. Run a time course the first time a new RNA species is tailed.

Tip: Over-tailing produces a heterogeneous smear on a gel — if that appears, cut the incubation time before changing anything else.

What it means: Cofactors Included lists the reaction components supplied alongside the enzyme. Here that is 1.0 ml of 10X reaction buffer plus 50 µl of 10 mM ATP.

Why it matters:

• ATP is the substrate for the reaction, not merely an energy source — without it no tail is added at all.
• Supplying ATP at a defined concentration means tail length can be reproduced between runs rather than varying with a lab stock of unknown age.
• The enzyme also requires Mg²⁺, which the supplied buffer provides; a chelator carried in with the RNA will stop the reaction.

How to interpret here: Use the supplied ATP rather than a general lab stock, and check that the RNA is not eluted in an EDTA-containing buffer that would sequester the magnesium.

Tip: ATP degrades with repeated freeze-thaw — aliquot the 50 µl on first use if the pack will be used over many sessions.