The A'-helix of CYP11A1 remodels mitochondrial cristae.

Background: CYP11A1 is a protein located in the inner membrane of mitochondria catalyzing the first step of steroid synthesis. As a marker gene for steroid-producing cells, the abundance of CYP11A1 characterizes the extent of steroidogenic cell differentiation. Besides, the mitochondria of fully differentiated steroidogenic cells are specialized with tubulovesicular cristae.

Function of CYP11A1 in the mitochondria.

Steroids are synthesized from the adrenal glands and gonads by enzymes of the cytochromes P450 and hydroxysteroid dehydrogenase in nature. These enzymes are located in the membrane of endoplasmic reticulum and mitochondria to catalyze redox reactions using electrons transported from the membrane. In the mitochondria, steroidogenic enzymes are inserted into the inner membrane with the bulk of the protein facing the matrix.

Conserved distal promoter of the agouti signaling protein (ASIP) gene controls sexual dichromatism in chickens.

Brilliant plumage is typical of male birds, thus sexual plumage dichromatism is seen in many avian species; however, the molecular mechanism underlying this remains unclear. The agouti signaling protein (ASIP) is a paracrine factor that stimulates yellow/red pigment (pheomelanin) synthesis and inhibits black/brown pigment (eumelanin) synthesis in follicular melanocytes. In mammals, the distal promoter of the ASIP gene acts exclusively on the ventral side of the body to create a countershading pigmentation pattern by stimulating pheomelanin synthesis in the ventrum.