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The conversion of the human membrane-associated folate binding protein (folate receptor) to the soluble folate binding protein by a membrane-associated metalloprotease.
J Biol Chem. 1991 Feb 05; 266(4):2346-53.JB

Abstract

The membrane-associated (M-FBP) and soluble (S-FBP) forms of human folate binding proteins (FBP) have been well characterized. Although related in a precursor-product manner, the mechanism of conversion and the basis for differences between M-FBP and S-FBP are not known. The conversion of M-FBP to S-FBP in crude human nasopharyngeal carcinoma (KB) cell preparations is demonstrated based on characteristic gel filtration elution profiles of M-FBP and S-FBP (Ve/V0 = 1.3 and 1.7, respectively) in Triton X-100. M-FBP is stoichiometrically converted to S-FBP in a time- and temperature-dependent reaction by a metalloprotease which is: heat-labile; particulate; contained in human KB cell and placental membranes, and rat kidney homogenates; inhibited by EDTA, 1,10-phenanthroline, and parahydroxymercuribenzoate; requires divalent cations; is maximally active at neutral pH; and is active in the presence or absence of detergent. The purified soluble FBP product appears to be identical to S-FBP. Conversion of purified endogenously [3H]leucine-labeled M-FBP yields a soluble FBP characterized by a 45% decrease in specific activity (moles of 3H/mol folate bound) relative to M-FBP and a non-folate binding fragment which contains 45% of the [3H]leucine from M-FBP, requires detergent and/or urea to remain soluble, and migrates aberrantly on gel filtration in 1% (v/v) Triton X-100 and 8 M urea. Based on changes in the specific activity and the gel filtration elution profiles of purified labeled M-FBP associated with conversion to S-FBP, the endoproteolytic cleavage site is predicted between residues 226 and 229 of the cDNA predicted human FBP amino acid sequence. These results suggest that the cDNA predicted hydrophobic carboxyl terminus (residues 227-257) remains intact on the fully processed, membrane-anchored M-FBP, contains the Triton binding domain, and is involved in the formation of the membrane anchor of M-FBP.

Authors+Show Affiliations

Medicine Branch, National Cancer Institute, Bethesda, Maryland 20892.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

1846624

Citation

Elwood, P C., et al. "The Conversion of the Human Membrane-associated Folate Binding Protein (folate Receptor) to the Soluble Folate Binding Protein By a Membrane-associated Metalloprotease." The Journal of Biological Chemistry, vol. 266, no. 4, 1991, pp. 2346-53.
Elwood PC, Deutsch JC, Kolhouse JF. The conversion of the human membrane-associated folate binding protein (folate receptor) to the soluble folate binding protein by a membrane-associated metalloprotease. J Biol Chem. 1991;266(4):2346-53.
Elwood, P. C., Deutsch, J. C., & Kolhouse, J. F. (1991). The conversion of the human membrane-associated folate binding protein (folate receptor) to the soluble folate binding protein by a membrane-associated metalloprotease. The Journal of Biological Chemistry, 266(4), 2346-53.
Elwood PC, Deutsch JC, Kolhouse JF. The Conversion of the Human Membrane-associated Folate Binding Protein (folate Receptor) to the Soluble Folate Binding Protein By a Membrane-associated Metalloprotease. J Biol Chem. 1991 Feb 5;266(4):2346-53. PubMed PMID: 1846624.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - The conversion of the human membrane-associated folate binding protein (folate receptor) to the soluble folate binding protein by a membrane-associated metalloprotease. AU - Elwood,P C, AU - Deutsch,J C, AU - Kolhouse,J F, PY - 1991/2/5/pubmed PY - 1991/2/5/medline PY - 1991/2/5/entrez SP - 2346 EP - 53 JF - The Journal of biological chemistry JO - J Biol Chem VL - 266 IS - 4 N2 - The membrane-associated (M-FBP) and soluble (S-FBP) forms of human folate binding proteins (FBP) have been well characterized. Although related in a precursor-product manner, the mechanism of conversion and the basis for differences between M-FBP and S-FBP are not known. The conversion of M-FBP to S-FBP in crude human nasopharyngeal carcinoma (KB) cell preparations is demonstrated based on characteristic gel filtration elution profiles of M-FBP and S-FBP (Ve/V0 = 1.3 and 1.7, respectively) in Triton X-100. M-FBP is stoichiometrically converted to S-FBP in a time- and temperature-dependent reaction by a metalloprotease which is: heat-labile; particulate; contained in human KB cell and placental membranes, and rat kidney homogenates; inhibited by EDTA, 1,10-phenanthroline, and parahydroxymercuribenzoate; requires divalent cations; is maximally active at neutral pH; and is active in the presence or absence of detergent. The purified soluble FBP product appears to be identical to S-FBP. Conversion of purified endogenously [3H]leucine-labeled M-FBP yields a soluble FBP characterized by a 45% decrease in specific activity (moles of 3H/mol folate bound) relative to M-FBP and a non-folate binding fragment which contains 45% of the [3H]leucine from M-FBP, requires detergent and/or urea to remain soluble, and migrates aberrantly on gel filtration in 1% (v/v) Triton X-100 and 8 M urea. Based on changes in the specific activity and the gel filtration elution profiles of purified labeled M-FBP associated with conversion to S-FBP, the endoproteolytic cleavage site is predicted between residues 226 and 229 of the cDNA predicted human FBP amino acid sequence. These results suggest that the cDNA predicted hydrophobic carboxyl terminus (residues 227-257) remains intact on the fully processed, membrane-anchored M-FBP, contains the Triton binding domain, and is involved in the formation of the membrane anchor of M-FBP. SN - 0021-9258 UR - https://www.unboundmedicine.com/medline/citation/1846624/The_conversion_of_the_human_membrane_associated_folate_binding_protein__folate_receptor__to_the_soluble_folate_binding_protein_by_a_membrane_associated_metalloprotease_ DB - PRIME DP - Unbound Medicine ER -