The N-terminal region of ABC50 interacts with eukaryotic initiation factor eIF2 and is a target for regulatory phosphorylation by CK2

Paytubi, Sonia, Morrice, Nicholas A., Boudeau, Jerome and Proud, Christopher G. (2008) The N-terminal region of ABC50 interacts with eukaryotic initiation factor eIF2 and is a target for regulatory phosphorylation by CK2. Biochemical Journal, 409 (1), 223-231. (doi:10.1042/BJ20070811). (PMID:17894550)

Abstract

ABC50 is an ABC (ATP-binding cassette) protein which, unlike most ABC proteins, lacks membrane-spanning domains. ABC50 interacts with eIF2 (eukaryotic initiation factor 2), a protein that plays a key role in translation initiation and in its control, and in regulation of ribosomes. Here, we establish that the interaction of ABC50 with eIF2 involves features in the N-terminal domain of ABC50, the region of ABC50 that differs most markedly from other ABC proteins. This region also shows no apparent similarity to the eIF2-binding domains of other partners of eIF2. In contrast, the N-terminus of ABC50 cannot bind to ribosomes by itself, but it can in conjunction with one of the nucleotide-binding domains. We demonstrate that ABC50 is a phosphoprotein and is phosphorylated at two sites by CK2. These sites, Ser-109 and Ser-140, lie in the N-terminal part of ABC50 but are not required for the binding of ABC50 to eIF2. Expression of a mutant of ABC50 in which both sites are mutated to alanine markedly decreased the association of eIF2 with 80S ribosomal and polysomal fractions.

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