Purification and characterization of a recombinant human cripto-1 protein

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Cripto-1 (CR-1) is a novel protein with a modified EGF-like motif.
• CR-1 does not bind to known erb B type-1 receptor tyrosine kinase receptors.
• Understanding CR-1's biological effects and structure-function relationships is crucial for comparing it with other EGF family members.

Purpose of the Study:

• To express and purify a biologically active form of recombinant human CR-1 (rhCR-1).
• To define the biological effects of CR-1.
• To compare the structure-function relationships of CR-1 with other EGF family growth factors.

Main Methods:

• Expressed full-length rhCR-1 in E. coli, with expression limited to inclusion bodies.
• Developed a procedure for solubilization and refolding of rhCR-1, involving chemical modification of cysteine residues.
• Purified the modified rhCR-1 using CM cation exchange and C4 reverse phase HPLC, followed by refolding in a redox buffer.

Main Results:

• High-level expression of rhCR-1 was achieved when fused to a histidine-tag.
• Chemical modification of cysteine residues facilitated solubilization and refolding of the aggregated protein.
• The refolded, modified rhCR-1 protein exhibited biological activity, including inhibition of beta-casein expression and promotion of mammary epithelial cell branching.

Conclusions:

• A method was established for producing biologically active, modified rhCR-1.
• The modified rhCR-1 protein shows significant biological functions relevant to growth factor activity.
• This work provides a foundation for further investigation into CR-1's role in biological processes.