# FOLATE BINDERS IN HEMATOPOIESIS AND CELL REPLICATION

> **NIH NIH R01** · SUNY DOWNSTATE MEDICAL CENTER · 1987 · $13,198

## Abstract

We have completed experiments which unambiguously established that rat
liver nuclei have receptors which bind the folate-binding protein (FBP)
purified from human chronic myelogenous leukemia cells.  Appropriate
controls were used in the experiments to show that granules alone did not
bind the FBP.  Standard kinetic studies and saturation analyses were
carried out using the FBP-[3H]-folate complex and 125I-FBP with the
nuclear preparation.  The following observations were made:  (1)\the nuclei
bind both the FBP-[3H]-folate complex and 125I-FBP at room temperature
and 4~C.  Binding is rapid, reaching near maximal values by 30 min; (2)\the
binding sites on the nuclei are saturable and by Scatchard analysis had a
kilodalton for the FBP-folate complex of 0.7 nM, with 1,000 binding sites
per nucleus; and (3)\the binding is inhibited by EDTA and this inhibition
is reversed by excess Ca2+ but not by Mg2+.

Two methods were used to ascertain the binding of the labeled FBP by the
solubilized nuclei: precipitation at 25% ethanol and gel-filtration through
Sephadex G-200.  Both methods show that a macromolecule solubilized from
the nuclei using Triton X-100 will bind the FBP-folate complex and this
binding is reversed by EDTA.  The problem, however, is that the yield is
very low and insufficient for further characterization of its properties.
For purification of the FBP from human tissues, we obtained spleens (either
autopsy or surgical discards) from patients with myeloproliferative
diseases.  The FBP protein in this tissue exists in two forms:  a small
cytosol protein (approximately 40 kilodaltons) and one which is membrane
bound (approximately 200 kilodaltons). We are now purifying each protein
from different fractions of the tissue homogenate.

Present objectives are:  (1)\purify to homogeneity the folate-binding
protein from human myeloproliferative tissue and determine its properties
and amino acid composition; (2)\solubilize and characterize the nuclear
receptor which binds the folate-binding protein; and (3)\determine the
conditions of intracellular folate metabolism, such as antifolate drugs or
folate deficiency, which modulate up or down the nuclear receptor for the
folate-binding protein.  (B)

## Key facts

- **NIH application ID:** 3170317
- **Project number:** 3R01CA032369-05S1
- **Recipient organization:** SUNY DOWNSTATE MEDICAL CENTER
- **SAM.gov UEI:** NJ14V2NZYM68
- **Principal Investigator:** SHELDON P ROTHENBERG
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 1987
- **Award amount:** $13,198
- **Award type:** 3
- **Project period:** 1982-05-01 → 1987-11-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/3170317

## Citation

> US National Institutes of Health, RePORTER application 3170317, FOLATE BINDERS IN HEMATOPOIESIS AND CELL REPLICATION (3R01CA032369-05S1). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/3170317. Licensed CC0.

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