Chou Y H, Hayman M J
Department of Microbiology, State University of New York, Stony Brook 11794.
Proc Natl Acad Sci U S A. 1991 Jun 1;88(11):4897-901. doi: 10.1073/pnas.88.11.4897.
We have screened cDNA libraries prepared from embryonic chicken tissues to isolate additional genes encoding growth factor receptors. Nucleotide sequencing of a cDNA encoding a gene, which we have termed klg, revealed it to represent an additional member of the immunoglobulin gene superfamily, which also possesses extensive sequence similarity to the protein-tyrosine kinase growth factor receptor genes. The klg gene was shown to encode a 140-kDa glycoprotein. However, the sequence of the tyrosine kinase domain is unusual in that the aspartate residue located within the highly conserved Asp-Phe-Gly triplet is replaced by an alanine residue. The presence of this aspartate has previously been found to be essential for tyrosine kinase activity. Consistent with the replacement of this aspartate, we were unable to detect any evidence of an associated kinase activity with the klg-encoded protein. These observations raise the possibility that the klg gene product represents a newly discovered class of receptor that plays a role in signal attenuation rather than signal propagation.
我们筛选了从鸡胚胎组织制备的cDNA文库，以分离出更多编码生长因子受体的基因。对一个我们称为klg的基因的cDNA进行核苷酸测序，结果显示它是免疫球蛋白基因超家族的另一个成员，并且与蛋白质酪氨酸激酶生长因子受体基因也具有广泛的序列相似性。klg基因被证明编码一种140 kDa的糖蛋白。然而，酪氨酸激酶结构域的序列并不寻常，因为位于高度保守的Asp-Phe-Gly三联体中的天冬氨酸残基被一个丙氨酸残基取代。此前已发现这种天冬氨酸的存在对于酪氨酸激酶活性至关重要。与这种天冬氨酸的取代一致，我们未能检测到任何与klg编码蛋白相关的激酶活性的证据。这些观察结果增加了一种可能性，即klg基因产物代表一种新发现的受体类别，它在信号衰减而非信号传播中发挥作用。
