So we’ll look at those shortly.
So when we start translating messenger RNA,
the ribosome is actually not assembled.
The small subunit will come
together with the large subunit
only once we have got messenger RNA
and the very first tRNA in place.
So let’s look at how that happens.
We have our small subunit.
We have our messenger RNA and we
have a charged tRNA ready to go.
Now, interestingly enough,
every messenger RNA and every gene will
begin with a tRNA that carries methionine.
So the first amino acid in every
single polypeptide is methionine
and that will generally get cut during
protein modification, so it may not –
the polypeptide chain may not end up
with a methionine at the very beginning,
but it will start that way
is what the ribosome needs
to get things going.
So all these components
and we invest a little bit of ATP
and use some initiation factors.
Initiation factors are other enzymes
that help the messenger RNA
and the first formylmethionine tRNA
gets arranged on the small subunit.
We put a little bit of energy in
and the anticodon of the first tRNA binds
with the start codon on the messenger RNA
and once this happens, we
have the initiation complex.
All together, the ribosomal
large subunit will come along
and join the party and we are ready to
begin the elongation phase of translation.