CLONING AND SEQUENCING OF THE CHICKEN EGG-WHITE AVIDIN-ENCODING GENE AND ITS RELATIONSHIP WITH THE AVIDIN-RELATED GENES AVR1-AVR5

The gene encoding chicken egg-white avidin (Avd) was amplified from ch romosomal DNA, cloned and sequenced. The entire coding region of preav idin (pre-Avd) containing four exons was identified by comparing the A vd gene (1119 bp) with the cDNA. It had a high identity percentage (91 -95%) with the previously isolated Avd-related genes 1-5 (Avr1-Avr5). Interestingly, comparison of Avd with the Avr genes showed that the in trons were better conserved (on average 97%) than the exons (90%). The Avd gene, as well as the cDNA, encodes a Gln residue at position 53 o f the mature protein, which is in contrast to the previously determine d amino-acid sequence.