Download MendeleyStructure dissection of zebrafish progranulins identifies a well-folded granulin/epithelin module protein with pro-cell survival activities.
Wang, P., Chitramuthu, B., Bateman, A., Bennett, H.P.J., Xu, P., Ni, F.(2018) Protein Sci 27: 1476-1490
- PubMed: 29732682
- DOI: https://doi.org/10.1002/pro.3441
- Primary Citation of Related Structures:
6CKU - PubMed Abstract:
The ancient and pluripotent progranulins contain multiple repeats of a cysteine-rich sequence motif of ∼60 amino acids, called the granulin/epithelin module (GEM) with a prototypic structure of four β-hairpins zipped together by six inter-hairpin disulfide bonds. Prevalence of this disulfide-enforced structure is assessed here by an expression screening of 19 unique GEM sequences of the four progranulins in the zebrafish genome, progranulins 1, 2, A and B. While a majority of the expressed GEM peptides did not exhibit uniquely folded conformations, module AaE from progranulin A and AbB from progranulin B were found to fold into the protopypic 4-hairpin structure along with disulfide formation. Module AaE has the most-rigid three-dimensional structure with all four β-hairpins defined using high-resolution (H- 15 N) NMR spectroscopy, including 492 inter-proton nuclear Overhauser effects, 23 3 J(HN,H α ) coupling constants, 22 hydrogen bonds as well as 45 residual dipolar coupling constants. Three-dimensional structure of AaE and the partially folded AbB re-iterate the conformational stability of the N-terminal stack of two beta-hairpins and varying degrees of structural flexibility for the C-terminal half of the 4-hairpin global fold of the GEM repeat. A cell-based assay demonstrated a functional activity for the zebrafish granulin AaE in promoting the survival of neuronal cells, similarly to what has been found for the corresponding granulin E module in human progranulin. Finally, this work highlights the remaining challenges in structure-activity studies of proteins containing the GEM repeats, due to the apparent prevalence of structural disorder in GEM motifs despite potentially a high density of intramolecular disulfide bonds.
Organizational Affiliation:
Department of Biochemistry, McIntyre Medical Sciences Building, McGill University, 3655 Promenade Sir William Osler, Montreal, Quebec, H3G 1Y6, Canada.
