Streptococcus gordonii expresses two related adhesins, SspA and SspB, the genes for which are adjacent on the chromosome and are regulated independently. Although the adhesins are functionally similar, the sspA promoter is more active than that of sspB. In this study we show an additional role for SspA in the control of sspB activity. Gel shift and DNA footprinting assays demonstrate that the S...

The RNA polymerase sigma factor SigF controls late development during sporulation in the filamentous bacterium Streptomyces coelicolor. The only known SigF-dependent gene identified so far, SCO5321, is found in the biosynthetic cluster encoding spore pigment synthesis. Here we identify the first direct target for SigF, the gene sspA, encoding a sporulation-specific protein. Bioinformatic analys...

The MglA protein is the only known regulator of virulence gene expression in Francisella tularensis, yet it is unclear how it functions. F. tularensis also contains an MglA-like protein called SspA. Here, we show that MglA and SspA cooperate with one another to control virulence gene expression in F. tularensis. Using a directed proteomic approach, we show that both MglA and SspA associate with...

In Francisella tularensis, the SspA protein family members MglA and SspA form a complex that associates with RNA polymerase (RNAP) to positively control the expression of virulence genes critical for the intramacrophage growth and survival of the organism. Although the association of the MglA-SspA complex with RNAP is evidently central to its role in controlling gene expression, the molecular d...

Orthologous proteins can be beneficial for X-ray crystallographic studies when a protein from an organism of choice fails to crystallize or the crystals are not suitable for structure determination. Their amino-acid sequences should be similar enough that they will share the same fold, but different enough so that they may crystallize under alternative conditions and diffract to higher resoluti...

The oral bacterium Streptococcus gordonii expresses two cell wall-associated polypeptides, designated SspA (1,542 amino acid residues) and SspB (1,462 amino acid residues), that have 70% sequence identity. These polypeptides are members of the antigen I/II family of oral streptococcal adhesins and mediate the binding of streptococci to salivary glycoproteins, collagen, and other oral microorgan...

1. Problem Statement and Objectives 1.1. Problem Statement 1.2. Objectives 1.2.1. Research Questions 1.3. Background 1.3.1. Trends in Geostationary Communication Satellite Design 1.3.1.1. What are power amplifiers? Why are they important? 1.3.1.2. Traveling Wave Tube Amplifiers 1.3.1.3. Solid State Power Amplifiers 1.3.1.4. SSPA vs. TWTA Space Technologies 1.3.2. Space Weather Phenomena 1.3.2.1...

The transcription factors MglA and SspA of Francisella tularensis form a heterodimer complex and interact with the RNA polymerase to regulate the expression of the Francisella pathogenicity island (FPI) genes. These genes are essential for this pathogen's virulence and survival within host cells. Our goal was to determine if an intracellular metabolite modulate these protein/protein interaction...

Motivated by recent advances in wideband-gap (WBG) gallium nitride (GaN) semiconductor technology, there is considerable interest in developing efficient solidstate power amplifiers (SSPAs) as an alternative to the traveling-wave tube amplifier (TWTA) for space applications. This article documents the general architecture considerations pertinent to developing SSPA architectures that can enable...

Stringent starvation protein A (SspA) of Escherichia coli is an RNA polymerase-associated transcriptional activator for the lytic development of phage P1 and is essential for stationary phase-induced acid tolerance of E. coli. We report the crystal structure of Yersinia pestis SspA, which is 83% identical to E. coli SspA in amino acid sequence and is functionally complementary in supporting the...