Immunoglobulin (Ig) domains are one of the most widespread protein domains encoded by the human genome and are present in a large array of proteins with diverse biological functions. These Ig domains possess a central structure, the immunoglobulin-fold, which is a sandwich of two β sheets, each made up of anti-parallel β strands, surrounding a central hydrophobic core. Apart from humans, proteins containing Ig-like domains are also distributed in a vast selection of organisms including vertebrates, invertebrates, plants, viruses and bacteria where they execute a wide array of discrete cellular functions. In this review, we have described the key structural deviations of bacterial Ig-folds when compared to the classical eukaryotic Ig-fold. Further, we have comprehensively grouped all the Ig-domain containing adhesins present in both Gram-negative and Gram-positive bacteria. Additionally, we describe the role of these particular adhesins in host tissue attachment, colonization and subsequent infection by both pathogenic and non-pathogenic Escherichia coli as well as other bacterial species. The structural properties of these Ig-domain containing adhesins, along with their interactions with specific Ig-like and non Ig-like binding partners present on the host cell surface have been discussed in detail.

中文翻译：

---

含免疫球蛋白的细菌粘附素折叠：宿主组织定植和感染的分子和结构观点

免疫球蛋白（Ig）结构域是人类基因组编码的最广泛的蛋白质结构域之一，存在于具有多种生物学功能的大量蛋白质中。这些Ig结构域具有一个中心结构，即免疫球蛋白折叠，它是两个β片的三明治，每个β片由反平行的β链组成，围绕着一个中心疏水核。除人类外，含有Ig样结构域的蛋白质还分布在多种生物中，包括脊椎动物，无脊椎动物，植物，病毒和细菌，它们在其中执行多种离散的细胞功能。在这篇综述中，我们描述了与经典的真核Ig折叠相比，细菌Ig折叠的关键结构偏差。进一步，我们将革兰氏阴性和革兰氏阳性细菌中所有包含Ig域的粘附素进行了全面分组。此外，我们描述了这些特定粘附素在宿主组织附着，定植和随后由致病性和非致病性感染中的作用大肠杆菌以及其他细菌种类。这些含Ig域的粘附素的结构特性，以及它们与宿主细胞表面上存在的特定Ig样和非Ig样结合伴侣之间的相互作用已得到详细讨论。