Febs Letters

doi: 10.1016/S0014-5793(06)00658-2pmid: N/A

doi: 10.1016/S0014-5793(06)00649-1pmid: N/A

Walma, Tine

doi: 10.1016/j.febslet.2006.05.024pmid: N/A

Shenoy, Avinash R.; Visweswariah, Sandhya S.

doi: 10.1016/j.febslet.2006.05.034pmid: 16730005

The conversion of adenine and guanine nucleoside triphosphates to cAMP and cGMP is carried out by nucleotide cyclases, which vary in their primary sequence and are therefore grouped into six classes. The class III enzymes encompass all eukaryotic adenylyl and guanylyl cyclase, and several bacterial and archaebacterial cyclases. Mycobacterial nucleotide cyclases show distinct biochemical properties and domain fusions, and we review here biochemical and structural studies on these enzymes from Mycobacterium tuberculosis and related bacteria. We also present an in silico analysis of nucleotide cyclases found in completely sequenced mycobacterial genomes. It is clear that this group of enzymes demonstrates the tinkering in the class III cyclase domain during evolution, involving subtle structural changes that retain the overall catalytic function and fine tune their activities.

Mitra, Kakoli; Frank, Joachim

doi: 10.1016/j.febslet.2006.05.019pmid: 16714018

The protein‐conducting channel (PCC) must allow both the translocation of soluble polypeptide regions across, and the lateral partitioning of hydrophobic transmembrane helices (TMHs) into, the membrane. We have analyzed existing structures of ribosomes and ribosome–PCC complexes and observe conformational changes suggesting that the ribosome may sense and orient the nascent polypeptide and also facilitate conformational changes in the PCC, subsequently directing the nascent polypeptide into the appropriate PCC‐mediated translocation mode. The PCC is predicted to be able to accommodate one central, consolidated channel or two segregated pores with different lipid accessibilities, which may enable the lipid‐mediated partitioning of a TMH from one pore, while the other, aqueous, pore allows translocation of a hydrophilic polypeptide segment. Our hypothesis suggests a plausible mechanism for the transitioning of the PCC between different configurations.

Antoun, Joseph; Amet, Yolande; Simon, Brigitte; Dréano, Yvonne; Corlu, Anne; Corcos, Laurent; Salaun, Jean Pierre; Plée-Gautier, Emmanuelle

doi: 10.1016/j.febslet.2006.05.006pmid: 16712844

CYP4A11, the major fatty acid ω‐hydroxylase in human liver is involved in the balance of lipids, but its role and regulation are both poorly understood. We studied the effects of retinoids on the regulation of CYP4A11 in the human hepatoma cell line HepaRG. Treatment of HepaRG cells with all‐trans‐retinoic acid resulted in a strong decrease in CYP4A11 gene expression and apoprotein content and, furthermore, was associated with a 50% decrease in the microsomal lauric acid hydroxylation activity. Such a strong suppression of CYP4A11 expression by retinoids could have a major impact on fatty acid metabolism in the liver.

Sakai, Hideki; Suzuki, Tomoyuki; Takahashi, Yuji; Ukai, Masashi; Tauchi, Katsunori; Fujii, Takuto; Horikawa, Naoki; Minamimura, Tetsuji; Tabuchi, Yoshiaki; Morii, Magotoshi; Tsukada, Kazuhiro; Takeguchi, Noriaki

doi:

Yasuda, Shingo; Taniguchi, Hiroyuki; Oceguera-Yanez, Fabian; Ando, Yoshikazu; Watanabe, Sadanori; Monypenny, James; Narumiya, Shuh

doi: 10.1016/j.febslet.2006.05.009pmid: 16716304

Here we used RNA interference and examined possible redundancy amongst Rho GTPases in their mitotic role. Chromosome misalignment is induced significantly in HeLa cells by Cdc42 depletion and not by depletion of either one or all of the other four Cdc42‐like GTPases (TC10, TCL, Wrch1 or Wrch2), four Rac‐like GTPases or three Rho‐like GTPases. Notably, combined depletion of Cdc42 and all of the other four Cdc42‐like GTPases significantly enhances chromosomal misalignment. These observations suggest that Cdc42 is the primary GTPase functioning during mitosis but that the other four Cdc42‐like GTPases can also assume the mitotic role in its absence.

McDearmon, Erin L.; Combs, Ariana C.; Sekiguchi, Kiyotoshi; Fujiwara, Hironobu; Ervasti, James M.

doi: 10.1016/j.febslet.2006.05.010pmid: 16709410

α‐Dystroglycan was quantitatively enriched from mammalian brain based on its uniform reactivity with Vicia villosa agglutinin and resolved into sub‐populations possessing or lacking the sulfated glucuronic acid epitope recognized by monoclonal antibody HNK‐1. We generated a new monoclonal antibody specific for a glycoepitope on brain α‐dystroglycan but absent from α‐dystroglycan expressed in all other tissues examined. Finally, we found that laminin‐10/11 preferentially bound to brain α‐dystroglycan compared to skeletal muscle α‐dystroglycan. Our results suggest that tissue‐specific glycosylation modifies the laminin binding specificity of α‐dystroglycan.

Christensen, Claus; Lauridsen, Jes B.; Berezin, Vladimir; Bock, Elisabeth; Kiselyov, Vladislav V.

doi: 10.1016/j.febslet.2006.05.008pmid: 16709412

The neural cell adhesion molecule (NCAM) can bind to and activate fibroblast growth factor receptor 1 (FGFR1). However, there are four major FGFR isoforms (FGFR1–FGFR4), and it is not known whether NCAM also interacts directly with the other three FGFR isoforms. In this study, we show by surface plasmon resonance analysis that NCAM can bind to FGFR2 with an affinity similar to that for the NCAM–FGFR1 interaction. However, the kinetic parameters for the NCAM–FGFR2 binding are different from those of the NCAM–FGFR1 binding. Both receptors were shown to cycle relatively fast between the NCAM bound and unbound states, although FGFR2 cycling was clearly faster (13 times) than the FGFR1 cycling. Moreover, ATP was more effective in inhibiting the binding of NCAM to FGFR1 than to FGFR2, indicating that the binding sites in NCAM for the two receptors are similar, but not identical.