G. Schultz - Böcker

With contributions by numerous experts

H. Wegele, L. Müller, and J. Buchner: Hsp70 and Hsp90 – A Relay Team for Protein Folding R. Schülein: The Early Stages of the Intracellular Transport of Membrane Proteins: Clinical and Pharmacological Implications L. Schild: The Epithelial Sodium Channel: From Molecule to Disease

The eukaryotic translation machinery must recognize the site on a messenger RNA (mRNA) where decoding should begin and where it should end. The selection of the translation start site is generally given by the ?rst AUG codon encoding the amino acid methionine. D- ing initiation soluble translation initiation factors (eukaryotic translation initiation factors [eIFs] in eukaryotes and prokaryotic translation initiation factors [IFs] in prokaryotes) bind the mRNA, deliver the initiator Met-tRNA, and assemble to form a complete 80S ribosome from the 40S and 60S subunits. By progressing along the mRNA in the 5 -to-3 direction the ribosome decodes the information and translates it into the polypeptide chain. During this process, repeated delivery of amino-acyl tRNA (aa-tRNA) to the ribosome, peptide bond formation, movement of the mRNA, and the growing peptidyl-tRNA is mediated by both soluble elongation factors (eukaryotic translation elongation factors [eEFs] in euka- otes and prokaryotic translation elongation factors [EFs] in prokaryotes) and the activity of the ribosome. The ?nal step in the translation process occurs when one of the three t- mination codons occupies the ribosomal A-site.Translation comes to an end and soluble release factors (eukaryotic translation termination factors [eRFs] in eukaryotes and proka- otic translation termination factors [RFs] in prokaryotes) facilitate hydrolytical release of the polypeptide chain (for recent reviews, see Inge-Vechtomov et al. 2003; Kisselev et al. 2003; Wilson and Nierhaus 2003; Kapp and Lorsch 2004).

Gastric acid plays a primary role in digestion as well as in the sterilization of food and water. Gastric juice contains the most concentrated physiological acid solution (pH~1) as a result + – of H and Cl ion secretion [hydrochloric acid (HCl) production] by parietal cells in the oxyntic mucosa of the stomach. The combined output of the parietal cells leads to the sec- tion of 1–2 l of HCl at a concentration of 150–160 mmol/l into the interior of the stomach. In order to facilitate the production of acid, the parietal cell relies on the generation of a high + concentration of H ions that are transported into the lumen of the gland. This process is fa- + + cilitated by activation of the gastric H ,K -ATPase, which translocates to the apical pole of + – the parietal cell. K as well as ATP hydrolysis and Cl all play critical roles in the activation + + of gastric H ,K -ATPase and are essential for the functioning of the enzyme (Reenstra and Forte 1990). This review will examine the classical proteins that have been linked to acid secretion as well as some recently identi?ed proteins that may modulate gastric acid secretion, in - dition we discuss the known secretagogues, and their receptors including a new receptor, which upon stimulation can lead to acid secretion.

With contributions by numerous experts

H. Wegele, L. Müller, and J. Buchner: Hsp70 and Hsp90 – A Relay Team for Protein Folding R. Schülein: The Early Stages of the Intracellular Transport of Membrane Proteins: Clinical and Pharmacological Implications L. Schild: The Epithelial Sodium Channel: From Molecule to Disease

The eukaryotic translation machinery must recognize the site on a messenger RNA (mRNA) where decoding should begin and where it should end. The selection of the translation start site is generally given by the ?rst AUG codon encoding the amino acid methionine. D- ing initiation soluble translation initiation factors (eukaryotic translation initiation factors [eIFs] in eukaryotes and prokaryotic translation initiation factors [IFs] in prokaryotes) bind the mRNA, deliver the initiator Met-tRNA, and assemble to form a complete 80S ribosome from the 40S and 60S subunits. By progressing along the mRNA in the 5 -to-3 direction the ribosome decodes the information and translates it into the polypeptide chain. During this process, repeated delivery of amino-acyl tRNA (aa-tRNA) to the ribosome, peptide bond formation, movement of the mRNA, and the growing peptidyl-tRNA is mediated by both soluble elongation factors (eukaryotic translation elongation factors [eEFs] in euka- otes and prokaryotic translation elongation factors [EFs] in prokaryotes) and the activity of the ribosome. The ?nal step in the translation process occurs when one of the three t- mination codons occupies the ribosomal A-site.Translation comes to an end and soluble release factors (eukaryotic translation termination factors [eRFs] in eukaryotes and proka- otic translation termination factors [RFs] in prokaryotes) facilitate hydrolytical release of the polypeptide chain (for recent reviews, see Inge-Vechtomov et al. 2003; Kisselev et al. 2003; Wilson and Nierhaus 2003; Kapp and Lorsch 2004).

Gastric acid plays a primary role in digestion as well as in the sterilization of food and water. Gastric juice contains the most concentrated physiological acid solution (pH~1) as a result + – of H and Cl ion secretion [hydrochloric acid (HCl) production] by parietal cells in the oxyntic mucosa of the stomach. The combined output of the parietal cells leads to the sec- tion of 1–2 l of HCl at a concentration of 150–160 mmol/l into the interior of the stomach. In order to facilitate the production of acid, the parietal cell relies on the generation of a high + concentration of H ions that are transported into the lumen of the gland. This process is fa- + + cilitated by activation of the gastric H ,K -ATPase, which translocates to the apical pole of + – the parietal cell. K as well as ATP hydrolysis and Cl all play critical roles in the activation + + of gastric H ,K -ATPase and are essential for the functioning of the enzyme (Reenstra and Forte 1990). This review will examine the classical proteins that have been linked to acid secretion as well as some recently identi?ed proteins that may modulate gastric acid secretion, in - dition we discuss the known secretagogues, and their receptors including a new receptor, which upon stimulation can lead to acid secretion.

Contents: R.L. Moss, G.M. Diffee, M.L. Greaser: Contractile Properties of Skeletal Muscle Fibers in Relation to Myofibrillar Protein Isoforms.-J.E. Wilson: Hexokinases.-J. Rassow, N. Pfanner: Molecular Chaperones and Intracellular Protein Translocation.- H. Fuder, E. Muscholl: Heteroreceptor-Mediated Modulation of Noradrenaline and Acetylcholine Release from Peripheral Nerves.

In the series Reviews of Physiology, Biochemistry and Pharmacology three excellent contributions by Ruth Heidelberger (Houston, TX, USA) with Electrophysiological Approaches to the Study of Neuronal Exocytosis and Synaptic Vesicle Dynamics and Kay Truscott et al. (Freiburg, Germany) with Transport of Proteins Into Mitochondria and Randall K. Powers and Marc D. Binder (Seattle, WA, USA) with Input-Output Functions of Mammalian Motoneurons form another outstanding volume.

The objectives in this special issue are (1) to critically review current information on the mechanisms coupling extracellular regulatory signals to regulation of cross-bridge cycling and proliferation in smooth muscle, and (2) identify significant gaps or unresolved issues that are important topics for future research. The experimental and analytical difficulties discussed above are increasingly recognized and surmounted. Elucidation of the molecular and cellular events underlying the biologal properties of smooth muscle is in the midst of a period of rapid progress. While the reviews reveal many gaps to be filled and illustrate areas of contention, they also capture the excitement of new discoveries.

Special Issue on the Tird Filament System