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1.
Proc Natl Acad Sci U S A ; 96(9): 4791-6, 1999 Apr 27.
Artículo en Inglés | MEDLINE | ID: mdl-10220372

RESUMEN

The TATA box-binding protein (TBP) is an essential component of the RNA polymerase II transcription apparatus in eukaryotic cells. Until recently, it was thought that the general transcriptional machinery was largely invariant and relied on a single TBP, whereas a large and diverse collection of activators and repressors were primarily responsible for imparting specificity to transcription initiation. However, it now appears that the "basal" transcriptional machinery also contributes to specificity via tissue-specific versions of TBP-associated factors as well as a tissue-specific TBP-related factor (TRF1) responsible for gene selectivity in Drosophila. Here we report the cloning of a TBP-related factor (TRF2) that is found in humans, Drosophila, Caenorhabditis elegans, and other metazoans. Like TRF1 and TBP, TRF2 binds transcription factor IIA (TFIIA) and TFIIB and appears to be part of a larger protein complex. TRF2's primary amino acid structure suggests divergence in the putative DNA binding domain, and not surprisingly, it fails to bind to DNA containing canonical TATA boxes. Most importantly, TRF2 is associated with loci on Drosophila chromosomes distinct from either TBP or TRF1, so it may have different promoter specificity and regulate a select subset of genes. These findings suggest that metazoans have evolved multiple TBPs to accommodate the vast increase in genes and expression patterns during development and cellular differentiation.


Asunto(s)
Proteínas de Unión al ADN/genética , TATA Box , Secuencia de Aminoácidos , Animales , Caenorhabditis elegans , Mapeo Cromosómico , Clonación Molecular , Drosophila , Humanos , Datos de Secuencia Molecular , Alineación de Secuencia , Análisis de Secuencia , Proteína 2 de Unión a Repeticiones Teloméricas , Transcripción Genética
2.
Biochemistry ; 35(44): 13922-8, 1996 Nov 05.
Artículo en Inglés | MEDLINE | ID: mdl-8909289

RESUMEN

HIV gp41 is the transmembrane glycoprotein responsible for fusion of viral and cellular membranes, enabling viral entry. The structure of gp41 was studied using two synthetic peptides derived from the ectodomain of gp41: a 38-residue peptide from the "heptad repeat" region (hr.wt), and a 34-residue peptide from a region closer to the C-terminus (bt wt). These peptides were found to form a trimer of heterodimers with approximately 80% alpha-helicity. To study their alignment, distances between spin-labels attached to Cys residues on Cys-substituted peptides were measured using a recently-developed electron paramagnetic resonance method [Rabenstein, M.D., & Shin, Y.-K. (1995) Proc Natl. Acad. Sci. U.S.A. 92, 8239-8243]. The heterotrimeric peptides were found to be antiparallel, consistent with a study on proteolytically cleaved peptide fragments of gp41 [Lu, M., Blacklow, S.C., & Kim, P.S. (1995) Nat. Struct. Biol. 2, 1075-1082]. Furthermore, the C-terminal 19 residues of hr.wt are not apposed to bt.wt, and 15 residues of bt.wt extend beyond the end of br.wt. Consistent with this alignment are tertiary interactions between specific sites of these peptides probed by spin-label mobility. Additionally, a second pair of peptides was studied. From the model, these are expected to align with complete overlap. Alone, neither was helical, but when mixed, they were 83% helical. Based on the alignment of the peptides, a model of the prefusogenic form of gp41 was constructed which is significantly different from the structure of influenza hemagglutinin.


Asunto(s)
Proteína gp41 de Envoltorio del VIH/química , VIH-1/química , Secuencia de Aminoácidos , Dicroismo Circular , Espectroscopía de Resonancia por Spin del Electrón , Proteína gp41 de Envoltorio del VIH/genética , VIH-1/genética , Glicoproteínas Hemaglutininas del Virus de la Influenza/química , Humanos , Modelos Moleculares , Datos de Secuencia Molecular , Estructura Molecular , Fragmentos de Péptidos/química , Fragmentos de Péptidos/genética , Estructura Terciaria de Proteína
3.
Proc Natl Acad Sci U S A ; 92(18): 8239-43, 1995 Aug 29.
Artículo en Inglés | MEDLINE | ID: mdl-7667275

RESUMEN

An EPR "spectroscopic ruler" was developed using a series of alpha-helical polypeptides, each modified with two nitroxide spin labels. The EPR line broadening due to electron-electron dipolar interactions in the frozen state was determined using the Fourier deconvolution method. These dipolar spectra were then used to estimate the distances between the two nitroxides separated by 8-25 A. Results agreed well with a simple alpha-helical model. The standard deviation from the model system was 0.9 A in the range of 8-25 A. This technique is applicable to complex systems such as membrane receptors and channels, which are difficult to access with high-resolution NMR or x-ray crystallography, and is expected to be particularly useful for systems for which optical methods are hampered by the presence of light-interfering membranes or chromophores.


Asunto(s)
Óxidos de Nitrógeno/química , Péptidos/química , Marcadores de Spin , Secuencia de Aminoácidos , Espectroscopía de Resonancia por Spin del Electrón , Electrones , Análisis de Fourier , Modelos Químicos , Datos de Secuencia Molecular
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