Distinct features of cap binding by eIF4E1b proteins.
Bottom Line: Moreover, eIF4E1b proteins are distinguishable from eIF4E1a by a set of conserved amino acid substitutions, several of which are located near to cap-binding residues.Indeed, eIF4E1b possesses several distinct features, namely, enhancement of cap binding by a benzyl group at N(7) position of guanine, a reduced response to increasing length of the phosphate chain and increased binding to a cap separated by a linker from Sepharose, suggesting differences in the arrangement of the protein's core.In agreement, mutagenesis of the amino acids differentiating eIF4E1b from eIF4E1a reduces cap binding by eIF4E1a 2-fold, demonstrating their role in modulating cap binding.
Affiliation: Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw 02-089, Poland. Electronic address: email@example.com.Show MeSH
Mentions: First, we compared the sequences of eight pairs of vertebrate eIF4E1a/eIF4E1b proteins (Fig. 1). The alignment indicates the α-helical and β-sheet regions that form the core of eIF4E1a proteins and the active-site residues, both for binding the 5′ cap, as well as eIF4G and 4E-BP [1,2]. Xenopus and human eIF4E1a share 84% identical residues, with the main differences located at the N-terminus and a few conservative point mutations dispersed through the rest of the proteins. Importantly, all residues participating in binding the cap and eIF4G are conserved (Fig. 1).
Affiliation: Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw 02-089, Poland. Electronic address: firstname.lastname@example.org.