Structure and expression of the cAMP cell-surface receptor

Area of Science:

• Molecular Biology
• Developmental Biology
• Cell Biology

Background:

• The cell surface receptor for cyclic AMP (cAMP) plays a crucial role in the early development of Dictyostelium discoideum.
• Understanding the molecular characteristics of this receptor is essential for deciphering developmental signaling pathways.

Purpose of the Study:

• To isolate and characterize the complementary DNAs (cDNAs) encoding the Dictyostelium discoideum cAMP cell surface receptor.
• To elucidate the structural features and potential membrane topology of the cAMP receptor.

Main Methods:

• Screening of lambda gt11 expression libraries using antibodies against the cAMP receptor.
• Verification of cDNA clone identity through beta-galactosidase fusion protein analysis, antibody purification, and nucleic acid hybridization.
• In vitro transcription and translation of isolated cDNAs.
• DNA sequencing and analysis of the deduced amino acid sequence.

Main Results:

• Isolation of multiple cDNAs corresponding to the cAMP receptor mRNA.
• Confirmation that the 2 kb mRNA hybridizes with cDNA probes and its abundance changes during development.
• The deduced amino acid sequence predicts a 392-amino acid protein with seven hydrophobic domains.
• A model suggesting seven transmembrane passes, similar to G-protein coupled receptors like rhodopsin.

Conclusions:

• The study successfully identified and characterized the Dictyostelium discoideum cAMP cell surface receptor at the molecular level.
• Structural analysis suggests the receptor is a seven-transmembrane protein, indicative of a conserved structural motif in cell surface signaling.
• The findings suggest a potential gene family of related surface receptors conserved across diverse species, including yeast and mammals.