Lutz-Freyermuth C, Query C C, Keene J D
Department of Microbiology and Immunology, Duke University Medical Center, Durham, NC 27710.
Proc Natl Acad Sci U S A. 1990 Aug;87(16):6393-7. doi: 10.1073/pnas.87.16.6393.
Many RNA-associated proteins contain a ribonucleoprotein (RNP) consensus octamer encompassed by a conserved 80 amino acid sequence, which we have termed an RNA recognition motif (RRM). RRM family members contain either one (class I) or multiple (class II) copies of this motif. We report here that a class II component of the U1 small nuclear RNP (snRNP), the A protein of U1 snRNP (U1snRNP-A), contains two RRMs (RRM1 and -2), yet has only one binding domain (RRM1) that interacts specifically with stem-loop II of U1 RNA. Quantitative analysis of binding affinities of fragments of U1snRNP-A demonstrated that an 86-amino acid polypeptide was competent to bind to U1 RNA with an affinity comparable to that of the full-length protein (Kd approximately 80 nM). The carboxyl-terminal RRM2 of U1snRNP-A did not bind to U1 RNA and may recognize an unidentified heterologous RNA. We propose that class II proteins may function as bridges between RNA components of RNP complexes such as the spliceosome.
许多与RNA相关的蛋白质都含有一个核糖核蛋白（RNP）共有八聚体，该八聚体被一个保守的80个氨基酸序列所包围，我们将其称为RNA识别基序（RRM）。RRM家族成员含有该基序的一个拷贝（I类）或多个拷贝（II类）。我们在此报告，U1小核核糖核蛋白（snRNP）的一个II类组分，即U1 snRNP的A蛋白（U1snRNP-A），含有两个RRM（RRM1和RRM2），但只有一个结合结构域（RRM1）能与U1 RNA的茎环II特异性相互作用。对U1snRNP-A片段结合亲和力的定量分析表明，一个86个氨基酸的多肽能够以与全长蛋白相当的亲和力结合U1 RNA（解离常数约为80 nM）。U1snRNP-A的羧基末端RRM2不与U1 RNA结合，可能识别一种未鉴定的异源RNA。我们提出，II类蛋白可能作为RNP复合物（如剪接体）的RNA组分之间的桥梁发挥作用。
