Abstract
An infant hamadryas baboon exhibiting an albino phenotype-white body hair and red eyes-was born to parents with wild-type body color. Pigmentation on some parts of its body surfaced during childhood and progressed with age. This baboon in adulthood has gray hair on parts of its body, such as the tail, distal portion of the legs, and face, with the remainder being white. This pigmentation pattern resembles that of the Siamese cat and the Himalayan variants of the mouse and the mink. The distinguishing phenotypes in these animals are known to be caused by a temperature-sensitive activity of tyrosinase, an enzyme essential for biosynthesis of melanin. We sequenced all the five exons of the tyrosinase (TYR) gene of this albino baboon, which were amplified by PCR, and found a base substitution leading to alteration of the 365th amino acid from Ala to Thr. Tyrosinase requires copper as a cofactor for its enzyme function. It has two copper-binding sites, the second of which contains His residues in positions 363 and 367 that are critical to its function. Thus, p.(Ala365Thr) due to a mutation in the TYR gene is a likely candidate for the cause of the albino phenotype in this baboon.
Highlights
Tyrosinase (EC 1.14.18.1) is an enzyme that catalyzes the tyrosine-to-dopa and dopa-to-dopaquinone reactions in melanin biosynthesis (Körner and Pawelek 1982) and is encoded by a single gene, TYR, in mice (Jiménez et al.1989) and other mammals
The parents of HamA produced 10 offspring, of which eight were wild-type and two were albino. These figures suggest that (i) there is a single locus that controls the wild-type/albino body color, (ii) the albino allele is recessive to the wild-type allele, (iii) the parents were both heterozygous, and (iv) HamA is homozygous for the albino allele
TYR gene of HamA carries a base substitution that leads to the amino acid alteration of p.(Ala365Thr)
Summary
Tyrosinase (EC 1.14.18.1) is an enzyme that catalyzes the tyrosine-to-dopa and dopa-to-dopaquinone reactions in melanin biosynthesis (Körner and Pawelek 1982) and is encoded by a single gene, TYR, in mice (Jiménez et al.1989) and other mammals. He exhibited a pigmentation pattern similar to that of the Siamese cat—gray hair on the tail, distal portion of legs, and face This coloration has been maintained until now (Fig. 1). Cima’s albino phenotype, we amplified all five exons of this gene by PCR using feces samples from both Cima and a wild-type hamadryas baboon and sequenced the fragments. This analysis revealed a mutation leading to an amino acid substitution, which is located in a functionally important region of the tyrosinase enzyme
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
