Domain structure, stability, and interactions of human complement C1.lovin.s: characterization of a derivative lacking most of the B chain

ABSTRACTImmunoglobulin (Ig) domains are the most prevalent protein domain structure and share a highly conserved folding pattern; however, this structural family of proteins is also the most diverse in terms of biological roles and tissue expression. Ig domains vary significantly in amino acid sequence but share a highly conserved tryptophan in the hydrophobic core of this beta-stranded protein. Palladin is an actin binding and bundling protein that has five Ig domains and plays an important role in normal cell adhesion and motility. Mutation of the core tryptophan in one Ig domain of palladin has been identified in a pancreatic cancer cell line, suggesting a crucial role for this sole tryptophan in palladin Ig domain structure, stability, and function. We found that actin binding and bundling was not completely abolished with removal of this tryptophan despite a partially unfolded structure and significantly reduced stability of the mutant Ig domain as shown by circular dichroism investigations. In addition, this mutant palladin domain displays a tryptophan-like fluorescence attributed to an anomalous tyrosine emission at 345 nm. Our results indicate that this emission originates from a tyrosinate that may be formed in the excited ground state by proton transfer to a nearby glutamyl residue. Furthermore, this study emphasizes the importance of tryptophan in protein structural stability and illustrates how tyrosinate emission contributions may be overlooked during the interpretation of the fluorescence properties of proteins.SHORT ABSTRACTThis study explores the functional and structural consequences of a point mutation in palladin, an Ig domain protein first identified in a pancreatic tumor cancer cell line. While exploring the consequences of mutating this conserved tryptophan in the hydrophobic core of the most prevalent domain structure found in proteins, an anomalous tyrosine fluorescence phenomenon was exposed.

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sRNA Target Prediction Organizing Tool (SPOT) Integrates Computational and Experimental Data To Facilitate Functional Characterization of Bacterial Small RNAs

mSphere ◽

10.1128/msphere.00561-18 ◽

2019 ◽

Vol 4 (1) ◽

Cited By ~ 4

Author(s):

Alisa M. King ◽

Carin K. Vanderpool ◽

Patrick H. Degnan

Keyword(s):

Experimental Data ◽

Stress Responses ◽

Small Rnas ◽

Metabolic Regulation ◽

Functional Characterization ◽

Target Prediction ◽

Structure Stability ◽

Accurate Identification ◽

Mrna Targets

Small RNAs (sRNAs) regulate gene expression in diverse bacteria by interacting with mRNAs to change their structure, stability, or translation. Hundreds of sRNAs have been identified in bacteria, but characterization of their regulatory functions is limited by difficulty with sensitive and accurate identification of mRNA targets. Thus, new robust methods of bacterial sRNA target identification are in demand. Here, we describe our small RNA target prediction organizing tool (SPOT), which streamlines the process of sRNA target prediction by providing a single pipeline that combines available computational prediction tools with customizable results filtering based on experimental data. SPOT allows the user to rapidly produce a prioritized list of predicted sRNA-target mRNA interactions that serves as a basis for further experimental characterization. This tool will facilitate elucidation of sRNA regulons in bacteria, allowing new discoveries regarding the roles of sRNAs in bacterial stress responses and metabolic regulation.

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Molecular Characterization of the Interaction of Borrelia parkeri and Borrelia turicatae with Human Complement Regulators

Infection and Immunity ◽

10.1128/iai.00089-10 ◽

2010 ◽

Vol 78 (5) ◽

pp. 2199-2208 ◽

Cited By ~ 16

Author(s):

Melanie Schott ◽

Sonja Grosskinsky ◽

Christiane Brenner ◽

Peter Kraiczy ◽

Reinhard Wallich

Keyword(s):

Binding Capacity ◽

Functional Characterization ◽

Ectopic Expression ◽

Factor H ◽

Human Complement ◽

Related Protein ◽

Relapsing Fever ◽

Extracellular Matrix Components ◽

Complement Regulators

ABSTRACT In North America, tick-borne relapsing fever is caused by the species Borrelia hermsii, B. parkeri, and B. turicatae, which are transmitted to humans through the bite of the respective infected tick vectors. Here we describe the identification and functional characterization of a surface lipoprotein of B. parkeri, designated BpcA, that binds the human complement regulators factor H and factor H-related protein 1 and, simultaneously, the host protease plasminogen. In contrast, the homologous B. turicatae protein failed to bind human factor H and factor H-related protein 1 but retained its plasminogen binding capacity. Factor H bound to BpcA maintains its regulatory capacity to control C3b deposition and C3 convertase activity. Ectopic expression of BpcA in a serum-sensitive B. burgdorferi strain protects transformed cells from complement-mediated killing. Furthermore, bound plasminogen/plasmin endows B. parkeri and B. turicatae with the potential to degrade extracellular matrix components. These findings expand our understanding of the putative recent evolutionary separation of Borrelia parkeri and Borrelia turicatae, provide evidence that B. parkeri differs from B. turicatae in its ability to resist complement attack, and may help in understanding the pathological processes underlying tick-borne relapsing fever.

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