The existence of homologies is explained by common ancestry, and according to modern definitions of homology, two structures in different species are homologous if they are derived from the same structure in the common ancestor.
Homology is a central concept of comparative and evolutionary biology, referring to the presence of the same bodily parts (e.g., morphological structures) in different species. Homology after the advent of evolutionary theoryĤ. Overall the data, combined with sequence analyses of 4EHP from evolutionary diverse species, strongly support the hypothesis that 4EHP plays a physiological role utilizing both cap-binding and protein-binding functions but which is distinct from eIF4E.ĭepartment of Chemistry, Nerviano Medical Sciences S.r.l., viale Pasteur 10, 20014 Nerviano, Milan, Italy.3. A peptide derived from the eIF4E inhibitory protein, 4E-BP1 binds h4EHP 100-fold less strongly than eIF4E but in a similar manner. In the absence of ligand the binding site is incompletely formed with one of the aromatic residues being disordered and the side-chain of the other adopting a novel conformation. The consequent conformational difference between the proteins allows the tyrosine to mimic the six-membered ring of the tryptophan in eIF4E and adopt an orientation that is similar to that seen for equivalent residues in other non-homologous cap-binding proteins. The tyrosine resides on a loop that is longer in h4EHP than in eIF4E.
m(7)GTP binds to 4EHP 200-fold more weakly than it does to eIF4E with the guanine base sandwiched by a tyrosine and a tryptophan instead of two tryptophan residues as seen in eIF4E. Here we use X-ray crystallography and isothermal titration calorimetry (ITC) to investigate further the binding of cap analogues and peptides to h4EHP. Like eIF4E it is able to bind the cap but it appears to play a different cellular role, possibly being involved in the fine-tuning of protein expression levels. Human 4EHP (h4EHP) is a homologue of eIF4E. In translation, the interaction between the cap and the eukaryotic initiation factor 4E (eIF4E) is important in the recruitment of the mRNAs to the ribosome. In addition to conferring stability to the mRNA, the cap is required for pre-mRNA splicing, nuclear export and translation by providing an anchor point for protein binding. Diversity, Equity, Inclusion, and AccessĪll eukaryotic cellular mRNAs contain a 5' m(7)GpppN cap.Citation, Usage, Privacy Policies, Logo.Biologically Interesting Molecule Reference Dictionary (BIRD).
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