2.A.2.4.14
Melanocyte-specific antigen or melanoma antigen, MatP, Slc45a2, Aim-1, AIM1, at the mouse underwhite locus.  Regulated by a melanocyte-specific transcription factor essential for pigmentation, MITF (Du and Fisher 2002). Mutations in MatP in humans cause oculocutaneous albinism type IV (OCA4), an autosomal recessive inherited disorder which is characterized by reduced biosynthesis of melanin pigmentation in skin, hair and eyes. The MATP protein consists of 530 amino acids which contains 12 TMSs (Kamaraj and Purohit 2016).  The D93N mutation causes oculocutaneous albinism 4 (OCA4), and the L374F mutatioin correlates with light pigmentation in European populations. Corresponding mutations were produced in the related and well-characterized sucrose transporter from rice, OsSUT1, and transport activity was measured by heterologous expression in Xenopus laevis oocytes and ¹⁴C-sucrose uptake in yeast. The D93N mutant had completly lost transport activity while the L374F mutant showed a 90% decrease in transport activity, although the substrate affinity was unaffected (Kamaraj and Purohit 2016).  Mutations in MATP protein showed loss of stability and became more flexible, which alter its structural conformation and function (Kamaraj and Purohit 2016).