Single base substitution in growth hormone receptor gene influences the receptor density in bovine liver.

OBJECTIVES: Nucleotide sequence polymorphisms in the coding gene regions may influence the biological properties of proteins encoded by a gene. The A/T substitution in exon 8 of the growth hormone receptor (GHR) gene results in changed amino acid sequence 279 (Phe/Tyr) in the transmembrane domain of the receptor protein and therefore could influence its functional parameters. We searched for the relationship between the A/T nucleotide polymorphism in the GHR gene the receptor binding capacity and dissociation constant. METHODS: Nucleotide sequence variations in the exon 8 (coding for the transmembrane domain of the receptor) of the bovine GHR gene and in fragments of adjacent introns were analysed using PCR-SSCP and sequencing techniques. GH receptor binding capacity (B max ) and dissociation constant (K d ) for GHR were determined by the Scatchard analysis in livers often bulls carrying the AA or AT GHR genotypes. RESULTS: Two single nucleotide polymorphisms (SNPs) were identified - the C/T transition in intron 8 at position 863+32 and the A/T transversion in exon 8 at position 836, the latter resulting in Phe/Tyr amino acid substitution in the receptor protein. The results showed significant differences in the GHR binding capacity between these genotypes. B max was significantly greater (p≤0.01) in bulls carrying TT genotype of GHR in comparison to those with the AT genotype. No significant differences in the dissociation constants (K d ) were found. CONCLUSION: Our results demonstrated that single base substitution in the transmembrane domain encoding region of GH receptor gene may influence the physiological properties of the receptor.