X-ray structure of the mature ectodomain of phogrin

• Published in: Journal of structural and functional genomics Vol. 16; no. 1; pp. 1 - 9
• Main Authors: Noguera, Martín E., Primo, María E., Jakoncic, Jean, Poskus, Edgardo, Solimena, Michele, Ermácora, Mario R.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.03.2015; Springer Nature B.V
• Subjects: Amino Acid Sequence; Binding Sites - genetics; Biochemistry; Bioinformatics; Biomedical and Life Sciences; Cell division; Cell growth; Crystallography, X-Ray; dense-core vesicle; Diabetes; Forestry Management; Glucose; Human Genetics; Hydrogen-Ion Concentration; Insulin; Life Sciences; Microbial Genetics and Genomics; Models, Molecular; Molecular Sequence Data; peptide hormone; Peptides; Phosphatase; Plant Genetics and Genomics; Protein Folding; Protein Multimerization; Protein Structure, Secondary; Protein Structure, Tertiary; Proteins; Receptor-Like Protein Tyrosine Phosphatases, Class 8 - chemistry; Receptor-Like Protein Tyrosine Phosphatases, Class 8 - genetics; Receptor-Like Protein Tyrosine Phosphatases, Class 8 - metabolism; secretory granule; Sequence Homology, Amino Acid; Signal transduction; Solutions; Structure-Activity Relationship; Secretory granule; Diabetes; Dense-core vesicle; Insulin; Peptide hormone
• ISSN: 1345-711X; 1570-0267
• DOI: 10.1007/s10969-014-9191-0

Phogrin/IA-2β and ICA512/IA-2 are two paralogs receptor-type protein-tyrosine phosphatases (RPTP) that localize in secretory granules of various neuroendocrine cells. In pancreatic islet β-cells, they participate in the regulation of insulin secretion, ensuring proper granulogenesis, and β-cell proliferation. The role of their cytoplasmic tail has been partially unveiled, while that of their luminal region remains unclear. To advance the understanding of its structure–function relationship, the X-ray structure of the mature ectodomain of phogrin (ME phogrin) at pH 7.4 and 4.6 has been solved at 1.95- and 2.01-Å resolution, respectively. Similarly to the ME of ICA512, ME phogrin adopts a ferredoxin-like fold: a sheet of four antiparallel β-strands packed against two α-helices. Sequence conservation among vertebrates, plants and insects suggests that the structural similarity extends to all the receptor family. Crystallized ME phogrin is monomeric, in agreement with solution studies but in striking contrast with the behavior of homodimeric ME ICA512. The structural details that may cause the quaternary structure differences are analyzed. The results provide a basis for building models of the overall orientation and oligomerization state of the receptor in biological membranes.