Roghani M, Lassarre C, Zapf J, Povoa G, Binoux M
Institut National de la Santé et de la Recherche Médicale, Hôpital Saint Antoine, Paris, France.
J Clin Endocrinol Metab. 1991 Sep;73(3):658-66. doi: 10.1210/jcem-73-3-658.
We have studied the relationships between the structure and affinity of two insulin-like growth factor-binding proteins (IGFBPs) purified from human cerebrospinal fluid (CSF). Competitive binding studies were performed using preparations of human recombinant IGF (rhIGF-I, rhIGF-II, and their labeled homologs) and the truncated variant form of IGF-I, rh-Des-(1-3)-IGF-I. One of these BPs, which is the most consistently detected in CSF, corresponds to IGFBP-2. The other is a new form whose N-terminal sequence we reported earlier, which we call the 32-30K BP on the basis of its electrophoretic migration. Comparisons were made with an IGFBP-1 preparation purified from amniotic fluid and with two BPs purified from human serum, which are homologous to the CSF BPs. The CSF BPs have particularly strong affinities for IGF-II. The estimated affinity constants (Ka) were 2 X 10(10) M-1 for IGFBP-2 and 10(11) M-1 for the 32-30K BP. These affinities were 15-20 and 70 times stronger than the respective affinities for IGF-I. The affinity of the 32-30K BP is the strongest among the BPs identified to date. The two BPs isolated from serum, which correspond to the 32-30K CSF BP and IGFBP-2, had affinities for IGF-II and IGF-I similar to those of the CSF BPs. IGFBP-1 had nearly identical affinities for the two IGFs of approximately 10(10) M-1. Des-(1-3)-IGF-I failed to bind to the CSF BPs, but bound to IGFBP-1, although with a 40-fold weaker affinity than IGF-I. From our data it would seem that IGFBP-1 has two classes of IGF-binding site, one of high and one of low (less than 10(9) M-1) affinity for both IGFs. The other two BPs, by contrast, each possess a predominant class of high affinity binding site for IGF-II. A second class of lower affinity (greater than 10(9) M-1) sites bind both IGF-I and IGF-II. In the case of the 32-30K BP, these preferentially bind IGF-II; in the case of IGFBP-2, their binding of the two IGFs is similar. These different types of binding site may play an important role in controlling the bioavailability of IGF-I and IGF-II.(ABSTRACT TRUNCATED AT 400 WORDS)
我们研究了从人脑脊液（CSF）中纯化得到的两种胰岛素样生长因子结合蛋白（IGFBPs）的结构与亲和力之间的关系。使用人重组IGF制剂（rhIGF-I、rhIGF-II及其标记的同源物）以及IGF-I的截短变体形式rh-Des-(1-3)-IGF-I进行了竞争性结合研究。其中一种在脑脊液中最常检测到的BP对应于IGFBP-2。另一种是我们之前报道过其N端序列的新形式，基于其电泳迁移率我们将其称为32 - 30K BP。将其与从羊水纯化得到的IGFBP-1制剂以及从人血清中纯化得到的两种与脑脊液BP同源的BP进行了比较。脑脊液BP对IGF-II具有特别强的亲和力。IGFBP-2的估计亲和常数（Ka）为2×10¹⁰ M⁻¹，32 - 30K BP的为10¹¹ M⁻¹。这些亲和力分别比它们对IGF-I的亲和力强15 - 20倍和70倍。32 - 30K BP的亲和力是迄今为止所鉴定的BP中最强的。从血清中分离出的两种BP，分别对应于32 - 30K脑脊液BP和IGFBP-2，它们对IGF-II和IGF-I的亲和力与脑脊液BP相似。IGFBP-1对两种IGF的亲和力几乎相同，约为10¹⁰ M⁻¹。Des-(1-3)-IGF-I未能与脑脊液BP结合，但能与IGFBP-1结合，不过其亲和力比IGF-I弱40倍。从我们的数据来看，IGFBP-1似乎有两类IGF结合位点，一类对两种IGF的亲和力高，另一类低（小于10⁹ M⁻¹）。相比之下，另外两种BP各自都有一类对IGF-II具有高亲和力的主要结合位点。另一类低亲和力（大于10⁹ M⁻¹）位点能结合IGF-I和IGF-II。就32 - 30K BP而言，这些位点优先结合IGF-II；就IGFBP-2而言，它们对两种IGF的结合情况相似。这些不同类型的结合位点可能在控制IGF-I和IGF-II的生物利用度方面发挥重要作用。（摘要截断于400字）
