title: A duplicated motif controls assembly of zona pellucida domain proteins.
abstract: Many secreted eukaryotic glycoproteins that play fundamental roles in development, hearing, immunity, and cancer polymerize into filaments and extracellular matrices through zona pellucida (ZP) domains. ZP domain proteins are synthesized as precursors containing C-terminal propeptides that are cleaved at conserved sites. However, the consequences of this processing and the mechanism by which nascent proteins assemble are unclear. By microinjection of mutated DNA constructs into growing oocytes and mammalian cell transfection, we have identified a conserved duplicated motif [EHP (external hydrophobic patch)/IHP (internal hydrophobic patch)] regulating the assembly of mouse ZP proteins. Whereas the transmembrane domain (TMD) of ZP3 can be functionally replaced by an unrelated TMD, mutations in either EHP or IHP do not hinder secretion of full-length ZP3 but completely abolish its assembly. Because mutants truncated before the TMD are not processed, we conclude that the conserved TMD of mammalian ZP proteins does not engage them in specific interactions but is essential for C-terminal processing. Cleavage of ZP precursors results in loss of the EHP, thereby activating secreted polypeptides to assemble by using the IHP within the ZP domain. Taken together, these findings suggest a general mechanism for assembly of ZP domain proteins.
authors.affiliation: Brookdale Department of Molecular, Cell, and Developmental Biology, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, NY 10029-6574, USA.
authors.forename: Luca
authors.initials: L
authors.lastname: Jovine
authors.forename: Huayu
authors.initials: H
authors.lastname: Qi
authors.forename: Zev
authors.initials: Z
authors.lastname: Williams
authors.forename: Eveline S
authors.initials: ES
authors.lastname: Litscher
authors.forename: Paul M
authors.initials: PM
authors.lastname: Wassarman
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D004527:Egg Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D006868:Hydrolysis; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D000072216:Zona Pellucida Glycoproteins
chemical_list: D004527:Egg Proteins; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; C000606517:ZP3 protein, human; D000072216:Zona Pellucida Glycoproteins; C000606521:Zp3 protein, mouse