Artikel-artikel Biologi Molekuler
Jurnal ini memuat berbagai informasi hasil penelitian terbaru di bidang biologi molekuler, untuk edisi 1 November 2007 sendiri ada beberapa isu terberu di bidang tersebut. Sayangnya jurnal ini The EMBO Journal tidak gratis, so cuma bisa membaca Abstraknya aja. Tapi untuk sekedar pengetahuan sudah cukup bagus...
Isu-isu terbaru 1 November 2007 antara lain :
Multifunctional class I transcription in Trypanosoma brucei depends on a novel protein complex
Jens Brandenburg, Bernd Schimanski, Everson Nogoceke, Tu N Nguyen, Júlio C Padovan, Brian T Chait, George A M Cross and Arthur Günzl The EMBO Journal advance online publication 1 November 2007;doi: 10.1038/sj.emboj.7601905
The vector-borne, protistan parasite Trypanosoma brucei is the only known eukaryote with a multifunctional RNA polymerase I that, in addition to ribosomal genes, transcribes genes encoding the parasite's major cell-surface proteins—the variant surface glycoprotein (VSG) and procyclin. In the mammalian bloodstream, antigenic variation of the VSG coat is the parasite's means to evade the immune response, while procyclin is necessary for effective establishment of trypanosome infection in the fly. Moreover, the exceptionally high efficiency of mono-allelic VSG expression is essential to bloodstream trypanosomes since its silencing caused rapid cell-cycle arrest in vitro and clearance of parasites from infected mice. Here we describe a novel protein complex that recognizes class I promoters and is indispensable for class I transcription; it consists of a dynein light chain and six polypeptides that are conserved only among trypanosomatid parasites. In accordance with an essential transcriptional function of the complex, silencing the expression of a key subunit was lethal to bloodstream trypanosomes and specifically affected the abundance of rRNA and VSG mRNA. The complex was dubbed class I transcription factor A.
Keywords: class I transcription factor, DYNLL1, procyclin, Tryponosoma brucei, VSG
A role for cytochrome c and cytochrome c peroxidase in electron shuttling from Erv1
Deepa V Dabir1, 6, Edward P Leverich1, 6, Sung-Kun Kim2, 5, Frederick D Tsai1, Masakazu Hirasawa2, David B Knaff2 and Carla M Koehler1, 3, 4 1 Department of Chemistry and Biochemistry, University of California at Los Angeles, Los Angeles, CA, USA2 Department of Chemistry and Biochemistry, Center for Biotechnology and Genomics, Texas Tech University, Lubbock, TX, USA3 Molecular Biology Institute, University of California at Los Angeles, Los Angeles, CA, USA4 Jonsson Comprehensive Cancer Center, University of California at Los Angeles, Los Angeles, CA, USA5 Department of Chemistry and Biochemistry, Baylor University, Waco, TX, USATo whom correspondence should be addressedCarla M Koehler, Department of Chemistry and Biochemistry, Molecular Biology Institute, Jonsson Comprehensive Cancer Center, Box 951569, University of California at Los Angeles, Los Angeles, CA 90095, USA. Tel.: +1 310 794 4834; Fax: +1 310 206 4038; E-mail: koehlerc@chem.ucla.edu
Erv1 is a flavin-dependent sulfhydryl oxidase in the mitochondrial intermembrane space (IMS) that functions in the import of cysteine-rich proteins. Redox titrations of recombinant Erv1 showed that it contains three distinct couples with midpoint potentials of -320, -215, and -150 mV. Like all redox-active enzymes, Erv1 requires one or more electron acceptors. We have generated strains with erv1 conditional alleles and employed biochemical and genetic strategies to facilitate identifying redox pathways involving Erv1. Here, we report that Erv1 forms a 1:1 complex with cytochrome c and a reduced Erv1 can transfer electrons directly to the ferric form of the cytochrome. Erv1 also utilized molecular oxygen as an electron acceptor to generate hydrogen peroxide, which is subsequently reduced to water by cytochrome c peroxidase (Ccp1). Oxidized Ccp1 was in turn reduced by the Erv1-reduced cytochrome c. By coupling these pathways, cytochrome c and Ccp1 function efficiently as Erv1-dependent electron acceptors. Thus, we propose that Erv1 utilizes diverse pathways for electron shuttling in the IMS.
Keywords: mitochondria, protein import, protein translocation, redox chemistry
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