Fig. 3.

The modular (two domain) structure of the gamma-B crystallin and differential kinetics of its domain folding are reflected in the differential codon usage in its domains and non-uniform translation of the protein. a) Backbone/cartoon structure of bovine, Bos taurus, gamma-B crystallin (PDB ID 4GCR); N-terminal (fast folding) domain is in blue and C-terminal (slow folding) domain is in yellow; the linker connecting two domains is in red. b) Codon usage/frequency histogram. The N-terminal domain is (on average) encoded by more frequent codons in comparison with the C-terminal one. There is a clear boundary between the two domains. c) [³⁵S]-Autoradiogram of gamma-B crystallin in vitro translation products (from [138]), a = gamma-B crystallin after 15 min translation; b-d = nascent peptides prepared from polyribosome fractions after 5, 10, and 15 min of gamma-B translation, respectively; e = gamma-B N-terminal domain translated separately; f = gamma circularly permuated protein (gamma-CP) after 15 min translation; g-I = nascent peptides prepared from polyribosome fractions after 5, 10, and 15 min of gamma-CP translation. Major peptides are denoted with numbers according to their lengths (estimated from peptide molecular weights). Arrow indicates the pause in the interdomain (linker region). d) Schematic representation of the (expected) distribution of paused ribosomes in the case of wild-type and circularly permutated gamma-B crystallins. Increased residence time of a ribosome at particular positions along mRNA leads to increased accumulation of the nascent chains of the respective sizes.