Crystal structure of zebrafish complement 1qA globular domain

Abstract

C1q contains three globular domains (C1qgD) that are the key functional component of the classical complement system. C1qgD can interact with important immune molecules, including IgG and C-reactive protein (CRP) to form defense systems to protect animals. Here, the first nonmammalian structure, zebrafish C1qA globular domain (Dare-C1qAgD) was solved. Although the overall architecture of Dare-C1qAgD is similar to human C1qA, residues involved in C1qBgD, C1qCgD, and CRP binding are somewhat different while residues involved in IgG binding are not present in zebrafish. The structure gives insight into how human and fish C1qA evolved from an ancestral protein.

An Experimental Adult Zebrafish Model for Shigella Pathogenesis, Transmission, and Vaccine Efficacy Studies

“…In our experiments, secretion of TTSS effectors does not have sole control over Shigella virulence, since the Δ hfq strain still cannot cause massive damage in the fish. Shigella sonnei phase II has a different O-antigen profile ( 37 ), and we observed a 2- to 3-fold colonization decrease compared to that of the pathogenic SsI . Δ hfq mutants have been used successfully in previous studies as an immunogen that confers cross-protection ( 14 ).…”

“…Fish blood contains a complement system just as mammalian blood does. These complement factors are heat-labile and contain the same features as their mammalian counterparts, i.e., ability to lyse bacteria via classical pathway, among others ( 37 , 38 ). Here, immunized fish heart extract caused lysis of wild-type bacteria, and as a result, fewer bacteria were recovered.…”

Invertebrate C1q Domain-Containing Proteins: Molecular Structure, Functional Properties and Biomedical Potential

“…Currently, the crystal structures of important C1q domains from vertebrate C1qDC proteins have been described: C1q protein, adiponectin, cerebellin-1, caprin-2 [64][65][66][67], as well as several C1q-like vertebrate proteins were crystalized and investigated [68][69][70][71][72][73]. At the same time, the structural similarity of C1q with tumor necrosis factor (TNF) was initially noted, which was the reason for combining them into one C1q/TNF superfamily Currently, the crystal structures of important C1q domains from vertebrate C1qDC proteins have been described: C1q protein, adiponectin, cerebellin-1, caprin-2 [64][65][66][67], as well as several C1q-like vertebrate proteins were crystalized and investigated [68][69][70][71][72][73]. At the same time, the structural similarity of C1q with tumor necrosis factor (TNF) was initially noted, which was the reason for combining them into one C1q/TNF superfamily [65,74,75].…”