Protein-lipid interaction. Biophysical studies of (Ca2+ + Mg2+)-ATPase reconstituted systems

Differential scanning calorimetry, fluorescence spectroscopy and freeze-fracture electron microscopy have been applied to a study of the reconstituted Ca2+-ATPase proteins from sarcoplasmic reticulum when they are incorporated into pure lipid/water systems. The results obtained with these techniques have been used to examine the effects of this intrinsic protein upon the surrounding lipid at temperatures above and below the main lipid solid-fluid phase transition temperature (Tc). 1. Above this Tc value, the freeze-fracture data show that the proteins are randomly distributed within the plane of the bilayer. The fluorescence data show that as the protein content in the bilayer increases, so does the 'microviscosity'. 2. Below Tc the proteins occur in high protein to lipid patches, separate from the remaining crystalline lipid. The fluorescence data indicate that at these temperatures the presence of the protein causes a decrease in microviscosity, whilst the calorimetric data indicate a decrease in enthalpy of the main lipid transition. 3. A premelting of the high protein to lipid patches formed by phase separation within the lipid bilayers is indicated by the calorimetric and fluorescence data. This observation is used to rationalise the 'anomalous' properties of the dipalmitoyl phosphatidylcholine-ATPase of exhibiting activity at temperatures well below the lipid phase transition at 41 degrees C.     

Phenotypic integration of morphology and energetic performance under routine capacities: a study in the leaf-eared mouse Phyllotis darwini

A major goal of evolutionary physiology is to understand the intrinsic and the extrinsic factors that impose limitations on an animal’s energy budget. Although natural selection acts upon organismal traits such as performance (e.g., burst, sustained metabolic rates), from a mechanistic perspective, organismal performance results from the integrated functioning of different levels of biological organization. Hence, a better understanding of whole-animal performance must necessarily incorporate an explicit analysis of the integration between those different levels. Although this topic has been under intense scrutiny, overall there have been very few consistent patterns. Here, we explore the phenotypic integration between organ masses and the overall energy budget under routine capacities by statistically decomposing the covariance matrix (using path analysis and canonical correlation analysis) between organ masses and thermoregulatory burst and sustained metabolisms in cold acclimated individuals of Phyllotis darwini. Our results suggest that (a) central organs associated with the processing of food (cecum and liver), residuals (kidneys) and pumping of O₂ (heart) are tightly integrated to sustained expenditure and between themselves; (b) with the exception of the heart, central energy supplying organs are weakly related to burst expenditures; (c) sustained and burst metabolisms refer to complete different strategies and (d) basal metabolic rate is not related to any of the physiological or morphological traits considered in this study. Overall, our results support the hypothesis of an economic phenotype: animals maintain their excess capacities to face those critical extreme events, but their physiology and internal morphology are tightly integrated to function under routine needs.     

Primary structure of a pyrroloquinoline quinone (PQQ) containing peptide isolated from porcine kidney diamine oxidase

After treating porcine kidney diamine oxidase (PKDAO, EC 1.4.3.6) with the inhibitor 2,4-dinitrophenylhydrazine (DNPH), the enzyme was subjected to proteolysis with trypsin. The hydrolysate contained a peptide to which the C(5) hydrazone of PQQ and DNPH (PQQ-DNPH) was bound. The peptide was purified to homogeneity after which the amino acid sequence was determined. It appeared to consist of 11 amino acids, with PQQ bound to number eight. Further proteolysis of the peptide with aminopeptidase and carboxypeptidase gave a compound which was identical to a product prepared from coupling of PQQ-DNPH to lysine. Therefore, the cofactor in PKDAO has most probably an amide bond between one of its carboxylic acid groups with the epsilon-NH2 group of a lysine residue. Possibilities for attachment of the cofactor to the protein chain are discussed.     

Invasive grass causes biotic homogenization in wetland birds in a Lake Erie coastal marsh

Hydrobiologia - Plant invasions often lead to homogenization of plant communities, but the potential for homogenization of other trophic levels is understudied in many systems. Biotic communities...