Eukaryotic Translation Initiation

Rough script of mechanism:
This is a general scheme of translation initiation.  We start with the small subunit of the ribosome, the 40S subunit.  Now, normally we see this subunit paired with the larger 60S subunit.  In this case, the ribosomal subunits are kept separate by initiation factor 3.  This is important for initiating translation -- we want to keep the 40S unit separate until we are bound to the mRNA.
The next step is the delivery of the first tRNA, which is of course, carrying the amino acid methionine.  Initation factor 2 delivers this tRNA directly to the P site of the ribosome.
Next, we have initiation factor 4 come in and guide the entire complex, called the pre-initiation complex, to the mRNA.  Now, the preinitation complex doesn’t bind directly to the AUG start codon -- its actually nonspecific in binding, and it proceeds to scan the transcript to find the first start codon, which is an AUG.  Once the complex finds the AUG, the GTP attached to initiation factor 2 can be hydrolyzed, and eIF2 can dissociate.  
eIF3 dissociates next, allowing the large 60 subunit of the ribosome to bind.  
We’re now ready for elongation to begin.  elongation factor 1 alpha comes in carrying the second tRNA into the A site, and peptidyl transferase, a ribozyme, can create peptide bonds.  This last step is repeated, and each subsequent tRNA is brought in with elongation factor 1 to continue to form a growing polypeptide chain

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