Sequence and analysis of a plasmid-encoded mercury resistance operon from Mycobacterium marinum identifies MerH, a new mercuric ion transporter

In this study, we report the DNA sequence and biological analysis of a mycobacterial mercury resistance operon encoding a novel Hg²⁺ transporter. MerH was found to transport mercuric ions in Escherichia coli via a pair of essential cysteine residues but only when coexpressed with the mercuric reductase.     

A PATERNITY TEST CASE FOR THE KILLER WHALE (ORCINUS ORCA) BY DNA FINGERPRINTING

The minisatellite DNA profiles from four captive killer whales (two adult males, a female and her calf) were compared to determine paternity between two potential fathers. One of the males was clearly excluded, while the other shared all paternal bands with the calf. The background of this technique, and its potential applications in captive breeding programs and field studies are discussed.     

Biochemical characterization of acyl carrier protein (AcpM) and malonyl-CoA:AcpM transacylase (mtFabD), two major components of Mycobacterium tuberculosis fatty acid synthase II

Malonyl coenzyme A (CoA)-acyl carrier protein (ACP) transacylase (MCAT) is an essential enzyme in the biosynthesis of fatty acids in all bacteria, including Mycobacterium tuberculosis. MCAT catalyzes the transacylation of malonate from malonyl-CoA to activated holo-ACP, to generate malonyl-ACP, which is an elongation substrate in fatty acid biosynthesis. To clarify the roles of the mycobacterial acyl carrier protein (AcpM) and MCAT in fatty acid and mycolic acid biosynthesis, we have cloned, expressed, and purified acpM and mtfabD (malonyl-CoA:AcpM transacylase) from M. tuberculosis. According to the culture conditions used, AcpM was produced in Escherichia coli in two or three different forms: apo-AcpM, holo-AcpM, and palmitoylated-AcpM, as revealed by electrospray mass spectrometry. The mtfabD gene encoding a putative MCAT was used to complement a thermosensitive E. coli fabD mutant. Expression and purification of mtFabD resulted in an active enzyme displaying strong MCAT activity in vitro. Enzymatic studies using different ACP substrates established that holo-AcpM constitutes the preferred substrate for mtFabD. In order to provide further insight into the structure-function relationship of mtFabD, different mutant proteins were generated. All mutations (Q9A, R116A, H194A, Q243A, S91T, and S91A) completely abrogated MCAT activity in vitro, thus underlining the importance of these residues in transacylation. The generation and characterization of the AcpM forms and mtFabD opens the way for further studies relating to fatty acid and mycolic acid biosynthesis to be explored in M. tuberculosis. Since a specific type of FabD is found in mycobacterial species, it represents an attractive new drug target waiting to be exploited.     

Genetically stable picornavirus expression vectors with recombinant internal ribosomal entry sites

In many respects, picornaviruses are well suited for their proposed use as immunization vectors. However, their inherent genetic instability hinders application for prophylactic purposes. We demonstrate the improved expression and stability of a heterologous insert through a novel vector design strategy that partially replaces noncoding regulatory sequences with coding sequences for foreign gene products.     

Sequence and expression of the hunchback gene in Lucilia sericata: a comparison with other Dipterans

We have found that the hunchback (hb)gene from Lucilia sericata is conserved in its functional domains in comparison with related flies, although there is divergence in the protein outside these regions. The expression patterns of Lucilia hb in early embryos are broadly similar to other higher Dipterans. However, in the posterior region we report blastoderm and post-gastrulation expression patterns, which are diverged from Musca and Drosophila. These patterns are reminiscent of hb expression in more primitive insects and could be indicative of changes in the regulation of hb in Lucilia by the terminal system.