Crystal structure of the middle domain of human poly(A)-binding protein-interacting protein 1.
Lei, J., Mesters, J.R., Brunn, A., Hilgenfeld, R.(2011) Biochem Biophys Res Commun 408: 680-685
- PubMed: 21539810 
- DOI: https://doi.org/10.1016/j.bbrc.2011.04.088
- Primary Citation of Related Structures:  
3RK6 - PubMed Abstract: 
In eukaryotes, the poly(A)-binding protein (PABP) is one of the important factors for initiation of messenger RNA translation. PABP activity is regulated by the PABP-interacting proteins (Paips), which include Paip1, Paip2A, and Paip2B. Human Paip1 has three different isoforms. Here, we report the crystal structure of the middle domain of Paip1 isoform 2 (Paip1M) as determined by single-wavelength anomalous dispersion phasing. The structure reveals a crescent-shaped domain consisting of 10 α-helices and two antiparallel β-strands forming a β-hairpin. The 10 α-helices are arranged as five HEAT repeats which form a double layer of α helices with a convex and a concave surface. Despite low sequence identity, the overall fold of Paip1M is similar to the middle domain of human eIF4GII and yeast eIF4GI. Moreover, the amino-acid sequence motif and the local structure of eIF4G involved in binding of eIF4A, are conserved in Paip1. The structure reported here is the first of a member of the Paip family, thereby filling a gap in our understanding of initiation of eukaryotic mRNA translation in three dimensions.
Organizational Affiliation: 
Institute of Biochemistry, Center for Structural and Cell Biology in Medicine, University of Lübeck, Ratzeburger Allee 160, Lübeck, Germany.