Febs Letters

doi: 10.1016/0014-5793(93)80905-Apmid: N/A

Nilsson, Tommy; Slusarewicz, Paul; Hoe, Mee H.; Warren, Graham

doi: 10.1016/0014-5793(93)80906-Bpmid: 8370450

The surprising result that the spanning domain causes retention of proteins in the Golgi stack poses the question as to the actual mechanism. Here we present a simple model that might have general applicability.

Novoderezhkin, V.I.; Razjivin, A.P.

doi: 10.1016/0014-5793(93)80907-Cpmid: 8370458

A new model of the light‐harvesting antenna (core complex) of purple photosynthetic bacteria is proposed based on excitonic interactions in circular aggregates of bacteriochlorophyll molecules. The calculated absorbance difference spectra of circular aggregates demonstrate all special features observed in the experimental spectra of purple bacteria. In particular, the absorption changes with high amplitude of bleaching at the longwavelength side of the absorption band at different excitation energy are predicted.

Tyynelä, Jaana; Palmer, David N.; Baumann, Marc; Haltia, Matti

doi: 10.1016/0014-5793(93)80908-Dpmid: 8370464

We have isolated storage cytosomes from brain tissue of patients with infantile neuronal ceroid‐lipofuscinosis. The purified storage bodies were subjected to compositional analysis which revealed a high content of proteins, accounting for 43% of dry weight. Saposins A and D, also known as sphingolipid activator proteins (SAPs), were shown to constitute a major portion of the accumulated protein using gel electrophoresis and sequence analysis. This is the first time that saposins have been found to be stored in any form of neuronal ceroid‐lipofuscinosis.

Strasser, Peter; Gimona, Mario; Moessler, Herbert; Herzog, Monika; Small, J.Victor

doi: 10.1016/0014-5793(93)80909-Epmid: 8370452

Calponin is a smooth muscle specific, actin‐, tropomyosin‐ and calmodulin‐binding protein thought to be involved in some way in the regulation or modulation of contraction. Here we describe the cloning and bacterial expression of two calponin species from murine and porcine smooth muscle tissues. Primary and secondary structural analyses of the deduced amino acid sequences revealed a high degree of homology to avian calponin with the exception of a short and variable C‐terminal segment. The sequence data demonstrate that the two mammalian calponin variants do not arise via alternative splicing but are encoded by different genes.

Ning, Gang; Maunsbach, Arvid B.; Esmann, Mikael

doi: 10.1016/0014-5793(93)80910-Mpmid: 8396537

Membrane‐bound Na,K‐ATPase was digested with trypsin in the presence of Rb+ to form the stable 19‐kDa and smaller fragments of the α‐chain known to preserve occlusion of Rb+ (K+) or Na+. The trypsinized membranes obtained from pig kidney and shark rectal gland were analyzed by electron microscopy. Tryptic digestion preserved general membrane structure but removed both the surface particles observed by negative staining and the protruding cytoplasmic portion of the α‐subunit identified in thin sections. However, intramembrane particles defined by freeze‐fracture were preserved after trypsinization suggesting that the remaining membrane spanning protein fragments retain the native structure within the lipid bilayer after proteolysis.

Kuipers, Oscar P.; Rollema, Harry S.; de Vos, Willem M.; Siezen, Roland J.

doi: 10.1016/0014-5793(93)80911-Dpmid: 8370453

The DNA sequence encoding the leader peptide of the lantibiotic subtilin from Bacillus subtilis was fused to the sequence encoding pronisin Z, and this hybrid gene was expressed in a Lactococcus lactis strain that produces nisin A. This strain simultaneously secreted nisin A and a protein of approximately 6 kDa. Amino acid sequencing of the purified 6 kDa protein and structural analysis of its main tryptic fragment by two‐dimensional 1H‐NMR showed that it consists of the unmodified leader peptide of subtilin, without the N‐terminal methionine residue, linked to a fully matured nisin Z part. The hybrid protein and its main tryptic fragment [ITPQ]‐nisin Z, showed at least 200‐fold lower antimicrobial activities than nisin Z against three different indicator strains.

Ono, Taka-aki; Noguchi, Takumi; Inoue, Yorinao; Kusunoki, Masami; Yamaguchi, Hirotaka; Oyanagi, Hiroyuki

doi: 10.1016/0014-5793(93)80912-Epmid: 8396538

Flash‐induced changes of the Mn K‐edge absorption spectra have been studied in the oxygen‐evolving complex depleted of Ca. The Mn K‐edge energy for the Ca‐depleted S1‐state was lower by 1.5 eV than that for the normal S1‐state. The K‐edge energy upshifted by 1 eV after one flash, indicative of an oxidation of Mn. After two flashes, the K‐edge was elevated as well by 0.4 eV, and then reached a steady‐state high level after continuous illumination where the K‐edge energy was higher by 0.9 eV than that after one flash. The results indicate that the Mn‐cluster and/or its direct ligand could be oxidized up to two electrons but further events are blocked.

Lindstad, Rune I.; McKinley-McKee, John S.

doi: 10.1016/0014-5793(93)80913-Fpmid: 8370454

Methylglyoxal, 1,2‐propanediol and glycerol are shown to be substrates for sheep liver sorbitol dehydrogenase. With 1,2‐propanediol the enzymecatalyzed reaction occurs specifically with the R(−)‐enantiomer. The maximum velocities and the specificity constants obtained for the three‐carbon substrates are considerably lower than those reported previously for sorbitol, and suggest that rate‐determination is imposed by catalytic steps other than the enzyme‐coenzyme product dissociation. The present findings are discussed in terms of substrate specificity and stereospecificity, and may indicate novel aspects of sorbitol dehydrogenase function in relation to glucose metabolism and diabetic pathogenesis.

Vellekoop, P.; Lugones, L.; van Brederode, J.

doi: 10.1016/0014-5793(93)80914-Gpmid: 8370455

An UDP‐glucose:flavonoid, 7‐O‐glucosyltransferase, from Silene latifolia was isolated from petals and purified 450‐fold using a combination of gel‐filtration, affinity chromatography and anion‐exchange chromatography. Affinity chromatography on a phenyl‐Sepharose CL‐4B column in combination with elution with the substrate, isovitexin (6‐C‐glucosylapigenin), was an especially effective purification step. A purification factor between 10 and 20 could be reached using this column. A possible mechanism for the specific interaction of the enzyme with the phenyl‐Sepharose will be discussed. This method of purification may also be applicable to other enzymes which use aromatic compounds as substrates. On a SDS‐PAGE gel a band of 54 kDa, which co‐purified with enzyme activity, could be detected in the purest fraction.