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General Comment |
Identification of a novel apolipoprotein, ApoN, in ovarian follicular fluid.
O'Bryan MK, et al .
A novel apolipoprotein, designated ApoN, has been identified in bovine ovarian follicular fluid using chromatographic purification methods, amino acid sequence analysis, molecular biology and bioinformatics. The apolipoprotein is a hydrophobic 12 k protein processed from the C-terminus of a 29 k precursor expressed in a number of tissues, including the ovary, testis, the anterior chamber of the eye, skeletal muscle, uterus and liver. Bovine, porcine and murine ApoN display significant homology at the amino acid level across the entire precursor sequence. Surprisingly, there appears to be no orthologous protein in the human, although an APON-like pseudogene is found on chromosome 12. The N terminal fragment of the ApoN precursor shows significant homology with the N terminal sequence of the precursor of the cholesterol transport regulatory protein ApoF, but the corresponding C-terminal sequences of ApoN and ApoF possess no homology. ApoN is present in the HDL fraction of bovine serum and both the HDL and LDL fractions of bovine follicular fluid, and is found in several tissues that are associated with local immunological privilege. These data suggest that ApoN may play a role in steroidogenesis and/or immunoregulation in the gonads of non-human species, as well as similar roles in other tissues.
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