Caveolin, a protein component of caveolae membrane coats.

https://www.cell.com/trends/plant-science/pdf/S1360-1385(14)00030-2.pdf

Plant salt-tolerance mechanisms

The binding change mechanism for ATP synthase — Some probabilities and possibilities

The spectrin-based membrane skeleton of the humble mammalian erythrocyte has provided biologists with a set of interacting proteins with diverse roles in organization and survival of cells in metazoan organisms. This review deals with the molecular physiology of spectrin, ankyrin, which links spectrin to the anion exchanger, and two spectrin-associated proteins that promote spectrin interactions with actin: adducin and protein 4.1. The lack of essential functions for these proteins in generic cells grown in culture and the absence of their genes in the yeast genome have, until recently, limited advances in understanding their roles outside of erythrocytes. However, completion of the genomes of simple metazoans and application of homologous recombination in mice now are providing the first glimpses of the full scope of physiological roles for spectrin, ankyrin, and their associated proteins. These functions now include targeting of ion channels and cell adhesion molecules to specialized compartments within the plasma membrane and endoplasmic reticulum of striated muscle and the nervous system, mechanical stabilization at the tissue level based on transcellular protein assemblies, participation in epithelial morphogenesis, and orientation of mitotic spindles in asymmetric cell divisions. These studies, in addition to stretching the erythrocyte paradigm beyond recognition, also are revealing novel cellular pathways essential for metazoan life. Examples are ankyrin-dependent targeting of proteins to excitable membrane domains in the plasma membrane and the Ca(2+) homeostasis compartment of the endoplasmic reticulum. Exciting questions for the future relate to the molecular basis for these pathways and their roles in a clinical context, either as the basis for disease or more positively as therapeutic targets.

Spectrin and Ankyrin-Based Pathways: Metazoan Inventions for Integrating Cells Into Tissues

Casein kinase 2: an 'eminence grise' in cellular regulation?

Key steps in a plant's development and adaptation to the environment are the initiation and development of lateral roots (LRs). LR development is regulated by auxin, the major plant hormone promoting LR formation, its counteracting hormones cytokinin, and abscisic acid (ABA). Here, we show that mutating ABSCISIC ACID INSENSITIVE4 (ABI4), which encodes an ABA-regulated AP2 domain transcription factor, results in an increased number of LRs. We show that ABI4 is expressed in roots and that its overexpression impairs LR development. Root expression of ABI4 is enhanced by ABA, and cytokinin and is repressed by auxin. Using hormone response promoters, we show that ABI4 also affects auxin and cytokinin profiles in the root. Furthermore, LR development in abi4 mutants is not altered or inhibited by cytokinin or ABA. Expression of the auxin-efflux carrier protein PIN1 is reduced in ABI4 overexpressors, enhanced in abi4 mutants, and is less sensitive to inhibition by cytokinin and ABA in abi4 mutants than in wild-type plants. Transport levels of exogenously applied auxin were elevated in abi4 mutants and reduced in ABI4 overexpressors. We therefore suggest that ABI4 mediates ABA and cytokinin inhibition of LR formation via reduction of polar auxin transport and that the resulting decrease in root auxin leads to a reduction in LR development.

/pdf/abi4-mediates-abscisic-acid-and-cytokinin-inhibition-of-15bqe90en0.pdf

ABI4 Mediates Abscisic Acid and Cytokinin Inhibition of Lateral Root Formation by Reducing Polar Auxin Transport in Arabidopsis

Tomato (Lycopersicon esculantum) ASR1 (abscisic acid stress ripening protein), a small plant-specific protein whose cellular mode of action defies deduction based on its sequence or homology analyses, is one of numerous plant gene products with unknown biological roles that become over-expressed under water- and salt-stress conditions Steady-state cellular levels of tomato ASR1 mRNA and protein are transiently increased following exposure of plants to poly(ethylene glycol), NaCl or abscisic acid Western blot and indirect immunofluorescence analysis with anti-ASR1 antibodies demonstrated that ASR1 is present both in the cytoplasmic and nuclear subcellular compartments; approx one-third of the total ASR1 protein could be detected in the nucleus Nuclear ASR1 is a chromatin-bound protein, and can be extracted with 1 M NaCl, but not with 05% Triton X-100 ASR1, overexpressed in Escherichia coli and purified to homogeneity, possesses zinc-dependent DNA-binding activity Competitive-binding experiments and SELEX (systematic evolution of ligands by exponential enrichment) analysis suggest that ASR1 binds at a preferred DNA sequence

The water- and salt-stress-regulated Asr1 (abscisic acid stress ripening) gene encodes a zinc-dependent DNA-binding protein

ASR1 is a plant-specific, highly charged, low molecular weight polypeptide. Purified ASR1 was shown to posses sequence specific Zn 2+ + + -dependent DNA binding activity (Kalifa et al . Biochemical Journal 381, 373-378, 2004). Steady-state levels of tomato Asr1 mRNA and protein are transiently increased following exposure of plants to poly- ethylene glycol, NaCl or abscisic acid. The biological role of ASR1 could not be deduced from sequence analyses or sequence homologies. Tobacco plants over-expressing tomato ASR1 have a decreased rate of water loss and improved salt tolerance. Upon exposure to salt, ASR1- over-expressing plants accumulate less Na + + + and proline than wild-type plants, and also results in increased steady- state levels of other gene products under non-stressed plant growth conditions. Therefore, ASR1 is probably involved in the regulation of water- or salt-stress-modulated gene expression.

Over‐expression of the water and salt stress‐regulated Asr1 gene confers an increased salt tolerance

Clathrin-coated vesicles contain two protein kinase activities. Phosphorylation of clathrin beta-light chain by casein kinase II.

Abscisic acid stress ripening 1 (ASR1) is a low molecular weight plant-specific protein encoded by an abiotic stress-regulated gene. Overexpression of ASR1 in transgenic plants increases their salt tolerance. The ASR1 protein possesses a zinc-dependent DNA-binding activity. The DNA-binding site was mapped to the central part of the polypeptide using truncated forms of the protein. Two additional zinc-binding sites were shown to be localized at the amino terminus of the polypeptide. ASR1 protein is presumed to be an intrinsically unstructured protein using a number of prediction algorithms. The degree of order of ASR1 was determined experimentally using nontagged recombinant protein expressed in Escherichia coli and purified to homogeneity. Purified ASR1 was shown to be unfolded using dynamic light scattering, gel filtration, microcalorimetry, circular dichroism, and Fourier transform infrared spectrometry. The protein was shown to be monomeric by analytical ultracentrifugation. Addition of zinc ions resulted in a global change in ASR1 structure from monomer to homodimer. Upon binding of zinc ions, the protein becomes ordered as shown by Fourier transform infrared spectrometry and microcalorimetry, concomitant with dimerization. Tomato (Solanum lycopersicum) leaf soluble ASR1 is unstructured in the absence of added zinc and gains structure upon binding of the metal ion. The effect of zinc binding on ASR1 folding and dimerization is discussed.

Desiccation and Zinc Binding Induce Transition of Tomato Abscisic Acid Stress Ripening 1, a Water Stress- and Salt Stress-Regulated Plant-Specific Protein, from Unfolded to Folded State

Dudy Bar-Zvi

Papers

ABI4 Mediates Abscisic Acid and Cytokinin Inhibition of Lateral Root Formation by Reducing Polar Auxin Transport in Arabidopsis

The water- and salt-stress-regulated Asr1 (abscisic acid stress ripening) gene encodes a zinc-dependent DNA-binding protein

Over‐expression of the water and salt stress‐regulated Asr1 gene confers an increased salt tolerance

Clathrin-coated vesicles contain two protein kinase activities. Phosphorylation of clathrin beta-light chain by casein kinase II.

Desiccation and Zinc Binding Induce Transition of Tomato Abscisic Acid Stress Ripening 1, a Water Stress- and Salt Stress-Regulated Plant-Specific Protein, from Unfolded to Folded State