A single amino acid residue replacement in the β subunit of human chorionic gonadotrophin results in the loss of biological activity

ABSTRACT The heterodimer, human chorionic gonadotrophin (hCG), contains an a subunit that is common to the glycoprotein hormones and a hormone-specific β subunit. A comparison of all known β amino acid sequences shows that an aspartic acid at position 99 (with the numbering scheme for hCG-β) is one of the seven non-Cys invariant residues. Using site-directed mutagenesis we have replaced hCG-β Asp99 with Arg. Chinese hamster ovary cells, containing a stably integrated gene for bovine a subunit, were transiently transfected with plasmids containing wild-type and mutant hCG-β cDNAs. The Arg99 β mutant associated with the a subunit, but the resulting heterodimer failed to enhance intracellular cyclic AMP production in a gonadotrophin-responsive transformed murine Leydig cell line. Thus, a single amino acid residue replacement in this glycosylated heterodimer containing 237 amino acid residues is sufficient to abolish activity.

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β-Endorphin: Deletion of a single amino acid residue abolishes immunoreactivity but retains opiate potency

Biochemical and Biophysical Research Communications ◽

10.1016/0006-291x(79)92014-x ◽

1979 ◽

Vol 87 (3) ◽

pp. 693-697 ◽

Cited By ~ 4

Author(s):

Choh Hao Li ◽

Wen-Chang Chang ◽

Donald Yamashiro ◽

Liang-Fu Tseng

Keyword(s):

Amino Acid ◽

Amino Acid Residue ◽

Single Amino Acid ◽

Single Amino Acid Residue

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Desaturase specificity is controlled by the physicochemical properties of a single amino acid residue in the substrate binding tunnel

Computational and Structural Biotechnology Journal ◽

10.1016/j.csbj.2020.05.011 ◽

2020 ◽

Vol 18 ◽

pp. 1202-1209

Author(s):

Aleš Buček ◽

Mario Vazdar ◽

Michal Tupec ◽

Aleš Svatoš ◽

Iva Pichová

Keyword(s):

Amino Acid ◽

Physicochemical Properties ◽

Amino Acid Residue ◽

Substrate Binding ◽

Single Amino Acid ◽

Single Amino Acid Residue

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Three Drosophila beta-tubulin sequences: a developmentally regulated isoform (beta 3), the testis-specific isoform (beta 2), and an assembly-defective mutation of the testis-specific isoform (B2t8) reveal both an ancient divergence in metazoan isotypes and structural constraints for beta-tubulin function.

Molecular and Cellular Biology ◽

10.1128/mcb.7.6.2231 ◽

1987 ◽

Vol 7 (6) ◽

pp. 2231-2242 ◽

Cited By ~ 72

Author(s):

J E Rudolph ◽

M Kimble ◽

H D Hoyle ◽

M A Subler ◽

E C Raff

Keyword(s):

Amino Acid ◽

Sequence Divergence ◽

Amino Acid Sequences ◽

Single Amino Acid ◽

Structural Constraints ◽

Wild Type ◽

Beta Tubulin ◽

Developmentally Regulated ◽

Single Amino Acid Residue ◽

Beta 2

The genomic DNA sequence and deduced amino acid sequence are presented for three Drosophila melanogaster beta-tubulins: a developmentally regulated isoform beta 3-tubulin, the wild-type testis-specific isoform beta 2-tubulin, and an ethyl methanesulfonate-induced assembly-defective mutation of the testis isoform, B2t8. The testis-specific beta 2-tubulin is highly homologous to the major vertebrate beta-tubulins, but beta 3-tubulin is considerably diverged. Comparison of the amino acid sequences of the two Drosophila isoforms to those of other beta-tubulins indicates that these two proteins are representative of an ancient sequence divergence event which at least preceded the split between lines leading to vertebrates and invertebrates. The intron/exon structures of the genes for beta 2- and beta 3-tubulin are not the same. The structure of the gene for the variant beta 3-tubulin isoform, but not that of the testis-specific beta 2-tubulin gene, is similar to that of vertebrate beta-tubulins. The mutation B2t8 in the gene for the testis-specific beta 2-tubulin defines a single amino acid residue required for normal assembly function of beta-tubulin. The sequence of the B2t8 gene is identical to that of the wild-type gene except for a single nucleotide change resulting in the substitution of lysine for glutamic acid at residue 288. This position falls at the junction between two major structural domains of the beta-tubulin molecule. Although this hinge region is relatively variable in sequence among different beta-tubulins, the residue corresponding to glu 288 of Drosophila beta 2-tubulin is highly conserved as an acidic amino acid not only in all other beta-tubulins but in alpha-tubulins as well.

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