Poly(A) Polymerase, Yeast

What it means: Source Organism is where the enzyme gene comes from. This poly(A) polymerase is from Saccharomyces cerevisiae, and behaves differently from the E. coli enzyme sold alongside it.

Why it matters:

• The yeast enzyme is particularly effective for oligonucleotide labelling and for poly(A) tailing of long RNA templates.
• The E. coli enzyme works sequence-independently on almost any accessible 3′ end, which suits mixed or unknown RNA pools better.
• Choosing the wrong one usually shows up as poor tailing efficiency rather than an outright failure, which makes it easy to misdiagnose.

How to interpret here: Pick the yeast enzyme for defined, long templates and for labelling short oligonucleotides. For heterogeneous RNA populations, compare against Poly(A) Polymerase, E. coli (Cat. No. E099).

Tip: The two enzymes use different cofactor packages — do not swap buffers between them.

What it means: Tailing Mechanism describes how the enzyme decides what to add. Template-independent means adenosine residues are added 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.
• Substituting cordycepin-5′-triphosphate (3′-dATP) for ATP stops the reaction after a single residue — a chain terminator lacking the 3′-OH needed to extend.

How to interpret here: Use ATP for a full tail and cordycepin triphosphate when you want exactly one dA added, for example in 3′-end labelling. Neither ADP nor dATP works as a substrate.

Tip: Run a time course the first time a new RNA species is tailed — over-tailing shows as a heterogeneous smear.

What it means: Cofactors Included lists the reaction components supplied with the enzyme. Here that is 500 µl of 25 mM MnCl₂ plus 150 µl of 10 mM ATP.

Why it matters:

• This enzyme uses manganese rather than magnesium — substituting a Mg²⁺-based buffer from another poly(A) polymerase will not work.
• ATP is the substrate, not merely an energy source; without it no tail is added at all.
• Supplying both at defined concentrations lets tail length be reproduced between runs instead of varying with lab stocks of unknown age.

How to interpret here: Use the supplied MnCl₂ and ATP rather than general lab stocks, and check that the RNA is not eluted in an EDTA-containing buffer, which would chelate the manganese.

Tip: Manganese oxidises in solution over time — keep the MnCl₂ tightly capped and discard visibly discoloured stock.

What it means: Buffer Included describes the reaction buffer supplied with the enzyme — 1.0 ml of 5X Poly(A) Polymerase, Yeast Reaction Buffer, matched to the 100 µl enzyme pack.

Why it matters:

• Poly(A) polymerase activity depends closely on salt and pH; a generic RNA-modifying enzyme buffer will not reproduce it.
• The matched buffer removes composition as a variable when tailing efficiency is lower than expected.
• Buffer volume is scaled to the enzyme pack, so nothing runs out mid-project.

How to interpret here: Dilute the 5X buffer five-fold in the final reaction, and add the MnCl₂ and ATP separately as the protocol directs — they are supplied as distinct components, not premixed into the buffer.

Tip: Thaw and mix the buffer completely before pipetting; components settle during frozen storage.