Since tyrosine phosphorylation appears to play important functions in photoreceptor cells, we searched here for retinal nonreceptor tyrosine kinases of the Src family. We demonstrated that Src family tyrosine kinases were present in the cytosolic fraction of extracted bovine retinas. A Src family tyrosine kinase with an apparent molecular mass of about 62 kDa was purified to homogeneity from the soluble fraction of dark-adapted bovine retinas after three consecutive purification steps: ω-aminooctyl-agarose hydrophobic chromatography, Cibacron blue 3GA-agarose pseudo-affinity chromatography, and α-casein-agarose affinity chromatography. The purified protein was subjected to N-terminal amino acid sequencing and the sequence Gly-Ile-Ile-Lys-Ser-Glu-Glu was obtained, which displayed homology with the first seven residues of the Src family tyrosine kinase c-Yes from Bos taurus (Gly-Cys-Ile-Lys-Ser-Lys-Glu). Although the cytosolic fraction from dark-adapted retinas contained tyrosine kinases of the Src family capable of phosphorylating the α-subunit of transducin, which is the heterotrimeric G protein involved in phototransduction, the purified tyrosine kinase was not capable of using transducin as a substrate. The cellular role of this retinal Src family member remains to be found.

中文翻译：

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从牛视网膜中纯化 Src 家族酪氨酸蛋白激酶

由于酪氨酸磷酸化似乎在感光细胞中发挥重要作用，我们在这里搜索了 Src 家族的视网膜非受体酪氨酸激酶。我们证明了 Src 家族酪氨酸激酶存在于提取的牛视网膜的细胞质部分中。经过三个连续纯化步骤后，表观分子量约为 62 kDa 的 Src 家族酪氨酸激酶从暗适应牛视网膜的可溶部分纯化至均质：ω-氨基辛基-琼脂糖疏水层析，Cibacron blue 3GA-琼脂糖假亲和层析和α-酪蛋白-琼脂糖亲和层析。纯化后的蛋白质进行N端氨基酸测序，得到序列Gly-Ile-Ile-Lys-Ser-Glu-Glu，它与来自 Bos taurus 的 Src 家族酪氨酸激酶 c-Yes (Gly-Cys-Ile-Lys-Ser-Lys-Glu) 的前七个残基具有同源性。虽然来自暗适应视网膜的胞质部分含有 Src 家族的酪氨酸激酶，能够磷酸化转导蛋白的 α-亚基，这是参与光转导的异源三聚体 G 蛋白，但纯化的酪氨酸激酶不能使用转导蛋白作为底物。这个视网膜 Src 家族成员的细胞作用仍有待发现。纯化的酪氨酸激酶不能使用转导蛋白作为底物。这个视网膜 Src 家族成员的细胞作用仍有待发现。纯化的酪氨酸激酶不能使用转导蛋白作为底物。这个视网膜 Src 家族成员的细胞作用仍有待发现。