Title

Intermolecular disulfide bonds are not required for the expression of the dimeric state and functional activity of the transferrin receptor

UMMS Affiliation

Department of Biochemistry; Program in Molecular Medicine

Publication Date

8-1-1989

Document Type

Article

Subjects

Animals; Antibodies, Monoclonal; Cell Line; Chemistry; Cricetinae; Cross-Linking Reagents; Cysteine; DNA; Disulfides; Electrophoresis, Polyacrylamide Gel; Gene Expression Regulation; Humans; Hydrogen-Ion Concentration; Kinetics; Macromolecular Substances; Mutation; Receptors, Transferrin; Serine; Structure-Activity Relationship; Transferrin

Disciplines

Life Sciences | Medicine and Health Sciences

Abstract

The human transferrin receptor is expressed as a disulfide-linked dimer at the cell surface. The sites of intermolecular disulfide bonds are Cys-89 and Cys-98. We have examined the functional significance of the covalent dimeric structure of the transferrin receptor by substitution of Cys-89 and Cys-98 with serine residues. Wild-type and mutated transferrin receptors were expressed in Chinese hamster ovary cells (clone TF-) that lack detectable endogenous transferrin receptors. The rates of receptor endocytosis and recycling were measured and the accumulation of iron by cells incubated with [59Fe]diferric transferrin was investigated. No significant differences between these rates were observed when cells expressing wild-type and mutated receptors were compared. The structure of the mutant receptor lacking intermolecular disulfide bonds was investigated. The presence of a population of mutant receptors with a non-covalent dimeric structure was indicated by cross-linking studies using diferric [125I]transferrin and the bifunctional reagent disuccinimidyl suberimidate. However, sucrose density gradient sedimentation analysis of Triton X-100 solubilized transferrin receptors demonstrated that the mutant receptor existed as a monomer in the absence of diferric transferrin and as an apparent dimer in the presence of this receptor ligand. We conclude that the covalent dimeric structure of the transferrin receptor is not required for the expression of the dimeric state and functional activity of the receptor.

Rights and Permissions

Citation: EMBO J. 1989 Aug;8(8):2231-40.

Related Resources

Link to Article in PubMed

Journal/Book/Conference Title

The EMBO journal

PubMed ID

2507316