UMMS Affiliation

Department of Biochemistry

Publication Date

4-1-1990

Document Type

Article

Subjects

Amino Acid Sequence; Animals; Cell Line; Cricetinae; Cysteine; Cytoplasm; DNA; *Endocytosis; Gene Expression; Humans; Molecular Sequence Data; *Mutation; Receptors, Transferrin; Sequence Homology, Nucleic Acid; Structure-Activity Relationship; Tyrosine

Disciplines

Biochemistry, Biophysics, and Structural Biology | Other Biochemistry, Biophysics, and Structural Biology

Abstract

The rate of receptor-mediated endocytosis of diferric 125I-transferrin by Chinese-hamster ovary cells expressing human transferrin receptors was compared with the rate measured for cells expressing hamster transferrin receptors. It was observed that the rate of endocytosis of the human transferrin receptor was significantly higher than that for the hamster receptor. In order to examine the molecular basis for the difference between the observed rates of endocytosis, a cDNA clone corresponding to the cytoplasmic domain of the hamster receptor was isolated. The predicted primary sequence of the cytoplasmic domain of the hamster transferrin receptor is identical with that of the human receptor, except at position 20, where a tyrosine residue in the human sequence is replaced with a cysteine residue. To test the hypothesis that this structural change in the receptor is related to the difference in the rate of internalization, we used site-directed mutagenesis to examine the effect of the replacement of tyrosine-20 with a cysteine residue in the human transferrin receptor. It was observed that the substitution of tyrosine-20 with cysteine caused a 60% inhibition of the rate of iron accumulation by cells incubated with [59Fe]diferric transferrin. No significant difference between the rate of internalization of the mutant (cysteine-20) human receptor and the hamster receptor was observed. Thus the substitution of tyrosine-20 with a cysteine residue can account for the difference between the rate of endocytosis of the human and hamster transferrin receptors.

Rights and Permissions

Citation: Biochem J. 1990 Apr 1;267(1):31-5.

Related Resources

Link to article in PubMed

Journal/Book/Conference Title

The Biochemical journal

PubMed ID

2327986

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