RESUMO
The transport of the CagA effector into gastric epithelial cells by the Cag Type IV secretion system (Cag T4SS) of Helicobacter pylori (H. pylori) is critical for pathogenesis. CagA is recruited to Cag T4SS by the Cagß ATPase. CagZ, a unique protein in H. pylori, regulates Cagß-mediated CagA transport, but the underlying mechanisms remain unclear. Here we report the crystal structure of the cytosolic region of Cagß, showing a typical ring-like hexameric assembly. The central channel of the ring is narrow, suggesting that CagA must unfold for transport through the channel. Our structure of CagZ in complex with the all-alpha domain (AAD) of Cagß shows that CagZ adopts an overall U-shape and tightly embraces Cagß. This binding mode of CagZ is incompatible with the formation of the Cagß hexamer essential for the ATPase activity. CagZ therefore inhibits Cagß by trapping it in the monomeric state. Based on these findings, we propose a refined model for the transport of CagA by Cagß.
Assuntos
Adenosina Trifosfatases , Proteínas de Bactérias , Helicobacter pylori , Adenosina Trifosfatases/metabolismo , Antígenos de Bactérias/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Helicobacter pylori/metabolismo , Sistemas de Secreção Tipo IV/metabolismoRESUMO
White spot syndrome virus (WSSV) is one of the major and most serious pathogen in the shrimp industry. As one of the most abundant envelope protein, VP24 acts as a core protein interacting with other structure proteins and plays an important role in virus assembly and infection. Here, we have presented the crystal structure of VP24 from WSSV. In the structure, VP24 consists of a nine-stranded ß-barrel fold with mostly antiparallel ß-strands, and the loops extending out the ß-barrel at both N-terminus and C-terminus, which is distinct to those of the other two major envelope proteins VP28 and VP26. Structural comparison of VP24 with VP26 and VP28 reveals opposite electrostatic surface potential properties of them. These structural differences could provide insight into their differential functional mechanisms and roles for virus assembly and infection. Moreover, the structure reveals a trimeric assembly, suggesting a likely natural conformation of VP24 in viral envelope. Therefore, in addition to confirming the evolutionary relationship among the three abundant envelope proteins of WSSV, our structural studies also facilitate a better understanding of the molecular mechanism underlying special roles of VP24 in WSSV assembly and infection.
Assuntos
Mutação , Proteínas do Envelope Viral/química , Proteínas do Envelope Viral/genética , Vírus da Síndrome da Mancha Branca 1/genética , Sequência de Aminoácidos , Animais , Clonagem Molecular , Cristalografia por Raios X , Modelos Moleculares , Penaeidae/virologia , Conformação Proteica , Multimerização Proteica , Homologia de Sequência de Aminoácidos , Proteínas do Envelope Viral/metabolismo , Vírus da Síndrome da Mancha Branca 1/metabolismo , Vírus da Síndrome da Mancha Branca 1/fisiologiaRESUMO
Human DAB2 interaction protein (DAB2IP) is a member of Ras-GTPase activating protein family and functions as a tumor suppressor, implying it could serve as a prognostic biomarker in cancers. Here we generated a mouse monoclonal antibody, 2A4, directed against human DAB2IP. This antibody was identified as IgG1 and specifically recognizes DAB2IP in both its native and denatured forms. It will serve as a useful and versatile tool for further mechanistic study and development of the potential prognostic significance of DAB2IP.
Assuntos
Anticorpos Monoclonais/imunologia , Proteínas Ativadoras de ras GTPase/imunologia , Animais , Biomarcadores Tumorais/imunologia , Linhagem Celular Tumoral , Feminino , Humanos , Imunoglobulina G/imunologia , Camundongos Endogâmicos BALB C , PrognósticoRESUMO
Helicobacter pylori is a well-known pathogen involved in the development of peptic ulcer, gastric adenocarcinoma and other forms of gastric cancer. Recently, there has been more considerable interest in strain-specific genes located in plasticity regions with great genetic variability. However, little is known about many of these genes. Studies suggested that certain genes in this region may play key roles in the pathogenesis of H. pylori-associated gastroduodenal diseases. JHP933, a conserved putative protein of unknown function, is encoded by the gene in plasticity region of H. pylori strain J99. Here we have determined the structure of JHP933. Our work demonstrates that JHP933 is a nucleotidyltransferase superfamily protein with a characteristic αßαßαßα topology. A superposition demonstrates overall structural homology of the JHP933 N-terminal fragment with lincosamide antibiotic adenylyltransferase LinA and identifies a possible substrate-binding cleft of JHP933. Furthermore, through structural comparison with LinA and LinB, we pinpoint conservative active site residues which may contribute to divalent ion coordination and substrate binding.