ABSTRACT
Entero virus 71 (EV71) causes hand, foot, and mouth disease (HFMD) and occasionally leads to severe neurological complications and even death. Scavenger receptor class B member 2 (SCARB2) is a functional receptor for EV71, that mediates viral attachment, internalization, and uncoating. However, the exact binding site of EV71 on SCARB2 is unknown. In this study, we generated a monoclonal antibody (mAb) that binds to human but not mouse SCARB2. It is named JL2, and it can effectively inhibit EV71 infection of target cells. Using a set of chimeras of human and mouse SCARB2, we identified that the region containing residues 77-113 of human SCARB2 contributes significantly to JL2 binding. The structure of the SCARB2-JL2 complex revealed that JL2 binds to the apical region of SCARB2 involving α-helices 2, 5, and 14. Our results provide new insights into the potential binding sites for EV71 on SCARB2 and the molecular mechanism of EV71 entry.
Subject(s)
Animals , Humans , Mice , Amino Acid Sequence , Antibodies, Monoclonal , Chemistry , Genetics , Metabolism , Binding Sites , Cell Line , Crystallography, X-Ray , Enterovirus A, Human , Genetics , Allergy and Immunology , Fibroblasts , Virology , Gene Expression , HEK293 Cells , Immunoglobulin Fab Fragments , Chemistry , Genetics , Metabolism , Lysosomal Membrane Proteins , Chemistry , Genetics , Allergy and Immunology , Models, Molecular , Protein Binding , Protein Conformation, alpha-Helical , Protein Conformation, beta-Strand , Protein Interaction Domains and Motifs , Receptors, Scavenger , Chemistry , Genetics , Allergy and Immunology , Receptors, Virus , Chemistry , Genetics , Allergy and Immunology , Recombinant Fusion Proteins , Chemistry , Genetics , Allergy and Immunology , Sequence Alignment , Sequence Homology, Amino Acid , Sf9 Cells , Spodoptera , ThermodynamicsABSTRACT
BACKGROUND: Physicochemical properties are frequently analyzed to characterize protein-sequences of known and unknown function. Especially the hydrophobicity of amino acids is often used for structural prediction or for the detection of membrane associated or embedded ß-sheets and α-helices. For this purpose many scales classifying amino acids according to their physicochemical properties have been defined over the past decades. In parallel, several hydrophobicity parameters have been defined for calculation of peptide properties. We analyzed the performance of separating sequence pools using 98 hydrophobicity scales and five different hydrophobicity parameters, namely the overall hydrophobicity, the hydrophobic moment for detection of the α-helical and ß-sheet membrane segments, the alternating hydrophobicity and the exact ß-strand score. RESULTS: Most of the scales are capable of discriminating between transmembrane α-helices and transmembrane ß-sheets, but assignment of peptides to pools of soluble peptides of different secondary structures is not achieved at the same quality. The separation capacity as measure of the discrimination between different structural elements is best by using the five different hydrophobicity parameters, but addition of the alternating hydrophobicity does not provide a large benefit. An in silico evolutionary approach shows that scales have limitation in separation capacity with a maximal threshold of 0.6 in general. We observed that scales derived from the evolutionary approach performed best in separating the different peptide pools when values for arginine and tyrosine were largely distinct from the value of glutamate. Finally, the separation of secondary structure pools via hydrophobicity can be supported by specific detectable patterns of four amino acids. CONCLUSION: It could be assumed that the quality of separation capacity of a certain scale depends on the spacing of the hydrophobicity value of certain amino acids. Irrespective of the wealth of hydrophobicity scales a scale separating all different kinds of secondary structures or between soluble and transmembrane peptides does not exist reflecting that properties other than hydrophobicity affect secondary structure formation as well. Nevertheless, application of hydrophobicity scales allows distinguishing between peptides with transmembrane α-helices and ß-sheets. Furthermore, the overall separation capacity score of 0.6 using different hydrophobicity parameters could be assisted by pattern search on the protein sequence level for specific peptides with a length of four amino acids.
Subject(s)
Hydrophobic and Hydrophilic Interactions , Amino Acids/chemistry , Membrane Proteins/chemistry , Reference Values , Time Factors , Weights and Measures , Algorithms , Predictive Value of Tests , Reproducibility of Results , Amino Acid Sequence , Protein Conformation, alpha-Helical , Protein Conformation, beta-Strand , Amino Acids/classificationABSTRACT
TRAF4 is a unique member of TRAF family, which is essential for innate immune response, nervous system and other systems. In addition to be an adaptor protein, TRAF4 was identified as a regulator protein in recent studies. We have determined the crystal structure of TRAF domain of TRAF4 (residues 292-466) at 2.60 Å resolution by X-ray crystallography method. The trimericly assembled TRAF4 resembles a mushroom shape, containing a super helical "stalk" which is made of three right-handed intertwined α helixes and a C-terminal "cap", which is divided at residue L302 as a boundary. Similar to other TRAFs, both intermolecular hydrophobic interaction in super helical "stalk" and hydrogen bonds in "cap" regions contribute directly to the formation of TRAF4 trimer. However, differing from other TRAFs, there is an additional flexible loop (residues 421-426), which contains a previously identified phosphorylated site S426 exposing on the surface. This S426 was reported to be phosphorylated by IKKα which is the pre-requisite for TRAF4-NOD2 complex formation and thus to inhibit NOD2-induced NF-κB activation. Therefore, the crystal structure of TRAF4-TRAF is valuable for understanding its molecular basis for its special function and provides structural information for further studies.
Subject(s)
Humans , Amino Acid Sequence , Binding Sites , Crystallography, X-Ray , Hydrophobic and Hydrophilic Interactions , Models, Molecular , Phosphorylation , Protein Conformation, alpha-Helical , Protein Domains , Protein Structure, Quaternary , Recombinant Proteins , Chemistry , Sequence Homology, Amino Acid , TNF Receptor-Associated Factor 4 , ChemistryABSTRACT
El éxito del tratamiento de las enfermedades infecciosas se ha visto comprometido en los últimos años debido a la diseminación de genes de resistencia a antibióticos entre las bacterias patógenas. Estos genes de resistencia a antibióticos son transportados por plásmidos, los cuáles son transferidos de una bacteria a otra mediante el proceso de conjugación. La reducción del uso inadecuado de los antibióticos y la búsqueda de inhibidores de la conjugación bacteriana son estrategias que podrían contribuir a la solución de este grave problema de salud pública. Basándose en la primera de esta estrategias, en enero de 2006 se regulo la dispensación de un grupo de antibióticos a fin de controlar su consumo. El análisis realizado en este trabajo seǹala que esta medida ha resultado ineficaz, puesto que el consumo y la resistencia bacteriana total a estos antimicrobianos se incrementó significativamente durante el periodo posterior a su promulgación. La resistencia bacteriana a muchas de las familias de antibióticos estudiadas esta solo parcialmente influenciada por su consumo, destacando la participación de otros factores, como la transferencia de genes de resistencia a antibióticos, en la prevalencia de cepas bacterianas resistentes. La identificación de proteínas del cito-cromo P450 de estructura y ligados conocidos, que tenían una similitud significativa en su secuencia de aminoácidos con la proteína de acoplamiento TRAG de los plásmidos R27 y R478, permitió identificar a los medicamentos diclofenac y ketoprofeno como potenciales inhibidores de la transferencia por conjugación de estos plásmidos. El modelado por homología de TRAG revelo que su dominio de solo hélices alfa podría ser el blanco de estos medicamentos. El ingreso de diclofenac o ketoprofeno a una cavidad en este dominio podría interferir en la interacción con el DNA portador de genes de resistencia a antibióticos que esta siendo transferido mediante el proceso de conjugación.