| Autor: |
Xiaoyang Qi, Ying Sun, Keiji Kondoh, Wen Qin, Gregory A. Grabowski |
| Rok vydání: |
1996 |
| Předmět: |
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| Zdroj: |
Journal of Biological Chemistry. 271:6874-6880 |
| ISSN: |
0021-9258 |
| DOI: |
10.1074/jbc.271.12.6874 |
| Popis: |
Saposin C is an essential co-factor for the hydrolysis of glucosylceramide by acid β-glucosidase in mammals. In addition, prosaposin promotes neurite outgrowth in vitro via sequences in saposin C. The regional organization of these neurotrophic and activation properties of saposin C was elucidated using recombinant or chemically synthesized saposin Cs from various regions of the molecule. Unreduced and reduced proteins were analyzed by electrospray-mass spectrometry to establish the complement of disulfide bonds in selected saposin Cs. Using saposin B as a unreactive backbone, chimeric saposins containing various length segments of saposin B and C localized the neurotrophic and acid β-glucosidase activation properties to the carboxyl- and NH2-terminal 50% of saposin C, respectively. The peptide spanning residues 22-31 had neurotrophic effects. Molecular modeling and site-directed mutagenesis localized the activation properties of saposin C to the region spanning residues 47-62. Secondary structure was needed for retention of this property. Single substitutions of R and S at the conserved cysteines at 47 or 78 diminished but did not obliterate the activation properties. These results indicate the segregation of neurotrophic and activation properties of saposin C to two different faces of the molecule and suggest a topographic sequestration of the activation region of prosaposin for protection of the cell from adverse hydrolytic activity of acid β-glucosidase. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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