Current Issues in Molecular Biology

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Nitrogen Fixation in Methanogens: The Archaeal Perspective

by John A. Leigh

Curr. Issues Mol. Biol. 2000, 2(4), 125-131; https://doi.org/10.21775/cimb.002.125 - 01 Oct 2000

Cited by 6 | Viewed by 1309

The methanogenic Archaea bring a broadened perspective to the field of nitrogen fixation. Biochemical and genetic studies show that nitrogen fixation in Archaea is evolutionarily related to nitrogen fixation in Bacteria and operates by the same fundamental mechanism. At least six nif genes present in Bacteria (nif H, D, K, E, N and X) are also found in the diazotrophic methanogens. Most nitrogenases in methanogens are probably of the molybdenum type. However, differences exist in gene organization and regulation. All six known nif genes of methanogens, plus two homologues of the bacterial nitrogen sensor-regulator glnB, occur in a single operon in Methanococcus maripaludis. nif gene transcription in methanogens is regulated by what appears to be a classical prokaryotic repression mechanism. At least one aspect of regulation, post-transcriptional ammonia switch-off, involves novel members of the glnB family. Phylogenetic analysis suggests that nitrogen fixation may have originated in a common ancestor of the Bacteria and the Archaea. Full article

1169 KiB

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Biological Membrane Structure by Solid-State NMR

by Michèle Auger

Curr. Issues Mol. Biol. 2000, 2(4), 119-124; https://doi.org/10.21775/cimb.002.119 - 01 Oct 2000

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Abstract

Nuclear magnetic resonance (NMR) spectroscopy, and particularly solid-state NMR spectroscopy, is a method of choice to study the structure and dynamics of both the lipid and the protein components of model and biological membranes. Different approaches have been developed to study these systems in which the restricted molecular motions result in broad NMR spectra. This contribution will first present an overview of the different techniques used to study lipid bilayers, namely ³¹P, ²H and ¹³C solid-state NMR spectroscopy. On the other hand, the study of the structure of membrane peptides and proteins is a rapidly growing field and several methods developed in the last two decades will be presented. These methods allow the investigation of protein systems for which structural information is often difficult to obtain by techniques such as X-ray diffraction and multidimensional solution NMR. Full article

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Ribozyme Pharmacokinetic Screening for Predicting Pharmacodynamic Dosing Regimens

by Tom J. Parry, Karyn S. Bouhana, Karin S. Blanchard, Pamela A. Pavco and Jennifer A. Sandberg

Curr. Issues Mol. Biol. 2000, 2(4), 113-118; https://doi.org/10.21775/cimb.002.113 - 01 Oct 2000

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Abstract

A significant amount of research has been devoted to the chemical stabilization of synthetic ribozymes, in part, so that applications to systemic disease can be explored. A nuclease-stabilized synthetic hammerhead ribozyme, ANGIOZYME, has been developed which targets the mRNA encoding a vascular endothelial growth factor receptor, Flt-1. Because the stimulation of this receptor may contribute to tumor neovascularization and subsequent tumor growth and metastasis, we have explored the systemic use of ANGIOZYME to down regulate this receptor in a syngeneic model of metastatic cancer. We describe here the application of pharmacokinetic analysis to the selection of a dosing regimen for pharmacodynamic screening in this murine cancer model. These studies demonstrate that the appropriate application of pharmacokinetic analysis is necessary for the optimization of systemic pharmacodynamic studies using synthetic ribozymes. Full article

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Molecular Mechanisms of Self-Incompatibility in Brassica

by Roman Sobotka, Lenka Sáková and Vladislav Curn

Curr. Issues Mol. Biol. 2000, 2(4), 103-112; https://doi.org/10.21775/cimb.002.103 - 01 Oct 2000

Viewed by 448

Abstract

In Brassica species, self-incompatibility has been mapped genetically to a single chromosomal location. In this region several closely linked genes have been identified. One of them, S-locus receptor kinase (SRK), determines Shaplotype specificity of the stigma and it's the key protein for SI reaction. The role of the Slocus glycoprotein (SLG) gene remains unclear. In the last decade approximately 15 additional genes linked to S-locus have been found. Recently, a gene has been identified (SCR) that encodes a small cysteine-rich protein which is a candidate for the pollen ligand. In addition to Slocus linked genes there are unlinked SLR genes (S-locus related genes). In this review, we discuss the role of these genes and the current view on the self-incompatibility mechanism in Brassica. Full article

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Curr. Issues Mol. Biol., Volume 2, Issue 4 (October 2000) – 4 articles

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