Shelton D L
Department of Neuroscience, Genentech, Inc., South San Francisco, CA 94080, USA.
Perspect Dev Neurobiol. 1996;4(1):101-7.
Ciliary neurotrophic factor (CNTF) and growth promoting activity (GPA) are two members of a family of structurally and functionally related cytokines. Although the primary sequences of these proteins are only distantly related, many share striking functional similarities. The question of the potential existence of more, as yet undiscovered, members of this family, especially those most related to CNTF, is discussed. There are several biological systems which exhibit unexplained CNTF-like activities. This has led to speculation that there are indeed other CNTF-like proteins to be found. Because of the poor primary sequence conservation among known members of this family, even those sharing strong functional similarities, it is unlikely that a cloning approach based on sequence homology will find these putative new members of the family. Instead, a more biological approach, based on functional similarities, is more likely to succeed.
睫状神经营养因子（CNTF）和生长促进活性（GPA）是结构和功能相关的细胞因子家族的两个成员。尽管这些蛋白质的一级序列只是远缘相关，但许多成员具有显著的功能相似性。本文讨论了该家族中可能存在更多尚未发现的成员的问题，尤其是那些与CNTF关系最为密切的成员。有几个生物系统表现出无法解释的CNTF样活性。这引发了人们的猜测，即确实还有其他CNTF样蛋白有待发现。由于该家族已知成员之间的一级序列保守性较差，即使是那些具有很强功能相似性的成员，基于序列同源性的克隆方法也不太可能找到该家族这些假定的新成员。相反，基于功能相似性的更具生物学特性的方法更有可能成功。
