The acrodermatitis enteropathica mutation affects protein expression in human fibroblasts: analysis by two-dimensional gel electrophoresis.

The acrodermatitis enteropathica (AE) mutation affects zinc uptake in human fibroblasts. However, the specific biochemical lesion has not been identified. We have used the technique of two-dimensional gel electrophoresis to identify protein differences in total cell lysate isolated from normal and AE fibroblasts. Two proteins with estimated molecular weights of 49.6 and 49.9 kDa and an isoelectric point of 5.1 were identified in normal fibroblasts but absent from AE fibroblasts. The proteins were purified, subjected to in-gel trypsin digest and the resulting peptides separated by HPLC. Sequences from three peptide fragments (8, 15 and 18 amino acids) were obtained after Edman degradation. None of the fragments exhibited homology to any amino acid sequences in the nonredundant Genbank database. The 15 and 18 amino acid fragments each exhibited 100% homology to a 136 amino acid expressed sequence tag that was homologous (43%) to adipophilin. However, the 15 and 18 amino acid fragments were only 30 and 44% homologous, respectively, to corresponding regions within the expressed sequence tag. Therefore, the 49.6/49.9 kDa protein absent from AE fibroblasts was not related to adipophilin. The 8 amino acid fragment did not exhibit homology to any expressed sequence tag. Therefore, the 49.6/49.9 kDa proteins are novel and may be the cause of the reduced zinc uptake and abnormal zinc metabolism characteristic of fibroblasts carrying the AE mutation.