Very few biological reactions occur spontaneously. In order for many of the essential functions of a cell to be met, the incorporation of many small factors is evident in many cell processes. The additional stages of the mechanism of translation initiation within eukaryotes is further advnaced through the utilization of many protein factors, of which ten are currently believed to be essential. Their importance can be seen in experiments in which a deficiency of one of these initiation factors (IF) can immensely reduce translation efficiency, if not stop it completely (Pestova and Hellen, 2000). Like prokaryotic initiation factors (IF), eIF (eukaryotic) have relatively the same functions, however with additional complexity. This extra level of complexity comes about due to the absence of a Shine-Delgano sequence to show the ribosomes where to start translating. Functions of eIFs are needed to target the 5'-end cap of an mRNA and bind a 40S ribosomal subunit nearby or to increase the rate of initiation.
With recent advancements in molecular technologies, all initiation factors have been sequenced and evidently their structures have been determined, with proposed functional activities being elucidated from mutational analysis (Pestova et al., 2000). Many of these initiation factors can be easily substituted from one eukaryotic species to another, in vivo, and still maintain functional activities. Conserved functional domains of many proteins are conserved through similar acitivities, as seen with RNA recognition motif (RRM) domains which are highly present in all RNA-protein binding factors. Fascinatingly, some eukaryotic initiation factors are even similar to prokaryotic initiation factors, displaying that there may be a conserved mechanism of translation initiation (Kozak 1999). I believe, a discussion of these factors, with recent discoveries into their roles within translation initiation, can further validate, strengthen or weaken the current models of translation initiation which will be discussed later on in the paper.