Climate change disrupts core habitats of marine species

Driven by climate change, marine biodiversity is undergoing a phase of rapid change that has proven to be even faster than changes observed in terrestrial ecosystems. Understanding how these changes in species composition will affect future marine life is crucial for conservation management, especially due to increasing demands for marine natural resources. Here, we analyse predictions of a multiparameter habitat suitability model covering the global projected ranges of >33,500 marine species from climate model projections under three CO₂ emission scenarios (RCP2.6, RCP4.5, RCP8.5) up to the year 2100. Our results show that the core habitat area will decline for many species, resulting in a net loss of 50% of the core habitat area for almost half of all marine species in 2100 under the high-emission scenario RCP8.5. As an additional consequence of the continuing distributional reorganization of marine life, gaps around the equator will appear for 8% (RCP2.6), 24% (RCP4.5), and 88% (RCP8.5) of marine species with cross-equatorial ranges. For many more species, continuous distributional ranges will be disrupted, thus reducing effective population size. In addition, high invasion rates in higher latitudes and polar regions will lead to substantial changes in the ecosystem and food web structure, particularly regarding the introduction of new predators. Overall, our study highlights that the degree of spatial and structural reorganization of marine life with ensued consequences for ecosystem functionality and conservation efforts will critically depend on the realized greenhouse gas emission pathway.     

βVI Turns in peptides and proteins: A model peptide mimicry

To investigate the role of proline in defining β turn conformations within cyclic hexa- and pentapeptides we synthesized and determined the conformations of a series of L - and D -proline-containing peptides by means of 2D NMR spectroscopy and restrained molecular dynamics simulations. Due to cis/trans isomerism the L -proline peptides adopt at least two different conformations that are analyzed and compared to the structures of the corresponding D -proline peptides. The cis conformations of the compounds cyclo(-Pro-Ala-Ala-Pro-Ala-Ala-), cyclo(-Arg-Gly-Asp-Phe-Pro-Gly-), cyclo(-Arg-Gly-Asp-Phe-Pro-Ala-), cyclo(-Pro-Ala-Ala-Ala-Ala--), and cyclo(-Pro-Ala-Pro-Ala-Ala-) form uncommon βVI turns that mimic the turn geometries found in crystallographically refined protein structures at such a detailed level that even preferred side chain orientations are reproduced. The ratios of the cis/trans isomers are analyzed in terms of the steric demand of the proline-following residue. The conformational details derived from this study illustrate the importance of the examination of small model compounds derived from protein loop regions, especially if bioactive recognition sequences, such as RGD (Arg-Gly-Asp), are incorporated. © 1993 Wiley-Liss, Inc.     

Physiologische Untersuchungen an einer ungewöhnlich säureresistenten Chlorella

Summary The influence of the hydrogen-ion concentration on the growth and metabolism of a highly acid-resistant green alga, Chlorella ellipsoidea (strain Marburg St), was studied. Chlorella pyrenoidosa (Emerson strain) served as a normal control organism. Growth of Chlorella ellipsoidea occurs in the entire range from Ph 2.0 to Ph 10, whereas for Chlorella pyrenoidosa the limits were found to be Ph 3.5 and Ph 10. Respiration is much less sensitive to hydrogen-ion concentration in the acid-resistant as compared to the normal strain. Thus an increase in acidity from Ph 4.0 to Ph 2.0 increases the respiratory oxygen uptake by 120% in Chlorella pyrenoidosa and by 25% in Chlorella ellipsoidea. In addition, only the less resistant Chlorella pyrenoidosa shows an accumulation of nitrite in the dark in acid culture media, indicating a disturbance of the normal course of nitrate reduction under these conditions. On the other hand, the rate of photosynthesis of both organisms was found to be almost independent of acidity between Ph 4.0 and Ph 2.0. At the acid and alkaline limits of growth in both algae, an inhibition of cell division leads to an increase of cell size and dry weight per cell, frequently connected with the occurrence of bizarre giant cells. — In addition, adaptation phenomena were found to play a role in determining the acid limit of growth. Cells of Chlorella ellipsoidea, after inoculation from normal medium (Ph about 6) into a solution of Ph 2.0, begin growth at a high rate only after a lag of about two weeks. Cells grown previously in an acid medium, however, immediately resume growth upon inoculation into a medium of Ph 2.0. This adaptation involves a considerable reduction of cell size.     

Determination of the phi angle in a peptide backbone by NMR spectroscopy with a combination of homonuclear and heteronuclear coupling constants.

The phi angle in a cyclic peptide is determined by the combined use of homonuclear and heteronuclear coupling constants. Two of the four coupling constants that define the phi angle in a peptide are determined exactly, two qualitatively. Via Karplus-type equations, they are transformed into dihedral angles and a good agreement is found, allowing for a determination of the phi angle with a certain range of degrees.     

On peptide bond formation, translocation, nascent protein progression and the regulatory properties of ribosomes. Derived on 20 October 2002 at the 28th FEBS Meeting in Istanbul.

High-resolution crystal structures of large ribosomal subunits from Deinococcus radiodurans complexed with tRNA-mimics indicate that precise substrate positioning, mandatory for efficient protein biosynthesis with no further conformational rearrangements, is governed by remote interactions of the tRNA helical features. Based on the peptidyl transferase center (PTC) architecture, on the placement of tRNA mimics, and on the existence of a two-fold related region consisting of about 180 nucleotides of the 23S RNA, we proposed a unified mechanism integrating peptide bond formation, A-to-P site translocation, and the entrance of the nascent protein into its exit tunnel. This mechanism implies sovereign, albeit correlated, motions of the tRNA termini and includes a spiral rotation of the A-site tRNA-3' end around a local two-fold rotation axis, identified within the PTC. PTC features, ensuring the precise orientation required for the A-site nucleophilic attack on the P-site carbonyl-carbon, guide these motions. Solvent mediated hydrogen transfer appears to facilitate peptide bond formation in conjunction with the spiral rotation. The detection of similar two-fold symmetry-related regions in all known structures of the large ribosomal subunit, indicate the universality of this mechanism, and emphasizes the significance of the ribosomal template for the precise alignment of the substrates as well as for accurate and efficient translocation. The symmetry-related region may also be involved in regulatory tasks, such as signal transmission between the ribosomal features facilitating the entrance and the release of the tRNA molecules. The protein exit tunnel is an additional feature that has a role in cellular regulation. We showed by crystallographic methods that this tunnel is capable of undergoing conformational oscillations and correlated the tunnel mobility with sequence discrimination, gating and intracellular regulation.     

A cyclophilin-like peptidyl-prolyl cis/trans isomerase from Legionella pneumophila – characterization, molecular cloning and overexpression

Legionella pneumophila is the causative agent of a severe form of pneumonia in humans (Legionnaires’disease). A major virulence factor, the Mip protein (FK506-binding protein, FKBP25mem), belongs to the enzyme family of peptidyl-prolyl cis/trans isomerases (PPIases). Here we show that L. pneumophila Philadelphia I possesses an additional cytoplasmic PPiase at a level of enzyme activity comparable to that of FKBP25mem. The N-terminal amino acid sequence of the purified protein was obtained by Edman degradation and showed that the protein is a member of the cyclophilin family of PPIases. The Icy gene (Legionella cycophn) was cloned and sequenced. It encodes a putative 164-amino-acid protein with a molecular mass of 17 968 Da called L. pneumophila cyclophilin 18 (L. p. Cyp18). Amino acid sequence comparison displays considerable similarity to the cytoplasmic and the periplasmic cyclophilins of Escherichia coll with 60.5% and 51.5% identity, respectively. The substrate specificity and inhibition by cyclosporin A revealed a pattern that is typically found for other bacterial cyclophilins. An L. pneumophila Cyp18 derivative with a 19-amino-acid polypeptide extension including a 6-histi-dine tag and an enterokinase cleavage site exhibits