0000000000458650
AUTHOR
Ismael Mingarro Muñoz
N-glycosylation efficiency is determined by the distance to the C-terminus and the amino acid preceding an Asn-Ser-Thr sequon
N-glycosylation is the most common and versatile protein modification. In eukaryotic cells, this modification is catalyzed cotranslationally by the enzyme oligosaccharyltransferase, which targets the β-amide of the asparagine in an Asn-Xaa-Ser/Thr consensus sequon (where Xaa is any amino acid but proline) in nascent proteins as they enter the endoplasmic reticulum. Because modification of the glycosylation acceptor site on membrane proteins occurs in a compartment-specific manner, the presence of glycosylation is used to indicate membrane protein topology. Moreover, glycosylation sites can be added to gain topological information. In this study, we explored the determinants of N-glycosylati…
Site-specificity of pea histone acetyltransferase B in vitro
Histone acetyltransferase B from pea embryonic axes has been purified approximately 300-fold by a combination of chromatographic procedures, including affinity chromatography on histone-agarose. The enzyme preparation has been used for the in vitro transfer of acetyl groups from [1-14C]acetyl-CoA to non-acetylated pea histone H4. Up to three acetyl groups can be introduced into the histone. The resulting mono-, di-, and triacetylated H4 isoforms were separated and sequenced to determine the acetylated sites. Only sites 5, 12, and 16 were used by histone acetyltransferase B, but no clear preference among them was observed. The absence of modification of other potentially acetylatable sites i…
Ala-insertion scanning mutagenesis of the glycophorin A transmembrane helix
Alanine insertions into the glycophorinA transmembrane helix are found to disrupthelix-helix dimerization in a way thatis fully consistentwith earlier saturation mutagenesis datas,uggesting that Ala-insertion scanning can be used to rapidly map the approximate locatiofn structurally and/or functionally importantsegments in trans-membrane helices
Membrane protein integration into the Endoplasmic Reticulum
Most integral membrane proteins are targeted, inserted and assembled in the endoplasmic reticulum (ER) membrane. The sequential and potentially overlapping events necessary for membrane protein integration take place at sites termed translocons, which comprise a specific set of membrane proteins acting in concert with ribosomes and, probably, molecular chaperones to ensure the success of the whole process. In this minireview, we summarize our current understanding of helical membrane protein integration at the endoplasmic reticulum, and highlight specific characteristics that affect the biogenesis of multispanning membrane proteins.
Caracterización y activación de enzimas lipolíticas en medios no acuosos
En primer lugar, en esta Tesis se ha explorado por primera vez, de una forma sistemática, el comportamiento de la fosfolipasa A2 de pancreas porcino (ppPLA2) en medios orgánicos monofásicos con bajo contenido en agua. Se ha investigado como pueden modular las actividades tanto desacilante como acilante de la enzima un número determinado de variables, encontrándose que: (i) la ppPLA2 es severamente inhibida por moderadas concentraciones de fosfolípidos sustrato y producto, lo que tiene implicaciones importantes, particularmente concernientes a su actividad sintética; (ii) la enzima exhibe una notable alteración de su selectividad hacia la cabeza polar de los sustratos con relación a la que m…