  Energy landscape theory describes how a full-length protein can attain its
native fold after sampling only a tiny fraction of all possible structures.
Although protein folding is now understood to be concomitant with synthesis on
the ribosome there have been few attempts to modify energy landscape theory by
accounting for cotranslational folding. This paper introduces a model for
cotranslational folding that leads to a natural definition of a nested energy
landscape. By applying concepts drawn from submanifold differential geometry
the dynamics of protein folding on the ribosome can be explored in a
quantitative manner and conditions on the nested potential energy landscapes
for a good cotranslational folder are obtained. A generalisation of diffusion
rate theory using van Kampen's technique of composite stochastic processes is
then used to account for entropic contributions and the effects of variable
translation rates on cotranslational folding. This stochastic approach agrees
well with experimental results and Hamiltionian formalism in the deterministic
limit.
