Characterization of the human prosaposin locus.
Item
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Title
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Characterization of the human prosaposin locus.
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Identifier
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AAI9304727
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identifier
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9304727
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Creator
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Rorman, Efrat Gavrieli.
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Contributor
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Adviser: Gregory A. Grabowski
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Date
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1992
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Genetics
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Abstract
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Many lysosomal hydrolases involved in the catabolism of complex sphingolipids require interactions with activator proteins for optimal hydrolytic activity. Such a small, heat stable, glycoprotein was described to enhance the hydrolytic rate of glucosyl ceramide by acid {dollar}\beta{dollar}-glucosidase in vitro. Abnormal enzymatic activity of acid {dollar}\beta{dollar}-glucosidase causes Gaucher disease. A similar disease is caused by the deficiency of the activator protein of acid {dollar}\beta{dollar}-glucosidase, saposin C. This work describes the cloning and characterization of a cDNA encoding four saposins, as well as the genomic organization of this locus. Based on the molecular data the following is presented: a model for the evolution of this gene, as well as the steps involved in maturation from prosaposin to four proteins and their functions.;Screening of two human cDNA libraries using mixed oligonucleotides encoding amino acid sequence of saposin C identified a 2767 bp long, full-length cDNA. This includes 38 bp of 5{dollar}\sp\prime{dollar} untranslated region, a 1672 bp open reading frame and 1157 bp of 3{dollar}\sp\prime{dollar} untranslated region. The coding region included a hydrophobic signal peptide and four, highly homologous, protein domains termed saposin A, B, C, and D which are proteolyticaly clipped from a precursor protein, prosaposin. An {dollar}\sim{dollar}80% amino acid similarity was found between prosaposin and a rat sertoli cell encoding sulfated glycoprotein-1. These results suggested that the human and rat genes derived from a single ancestral precursor. To examine this hypothesis the genomic organization of the human gene is described. A region of 19,985 bp-long which includes the four protein domains and the carboxy-terminus of the signal peptide was sequenced. This sequence comprised 13 exons ranging in size from 59 to 119 bp. Each of the intron/exon boundaries conformed to the gt/ag rules. Only two Alu consensus sequences were found. The location of the introns in respect to the exonic sequence was used to explain the evolution of this locus by duplication events and a double crossover.;The function of prosaposin is not known yet but, it might be involved in glycolipid binding and have a role in cell differentiation processes.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
