NMR assignment of M-crystallin: a novel Ca<SUP>2+</SUP> binding protein of the βγ-crystallin superfamily from Methanosarcina acetivorans

This article does not have an abstract

Solution structure and calcium-binding properties of M-crystallin, a primordial βγ-crystallin from archaea

The lens βγ-crystallin superfamily has many diverse but topologically related members belonging to various taxa. Based on structural topology, these proteins are considered to be evolutionarily related to lens crystallins, suggesting their origin from a common ancestor. Proteins with βγ-crystallin domains, although found in some eukaryotes and eubacteria, have not yet been reported in archaea. Sequence searches in the genome of the archaebacterium Methanosarcina acetivorans revealed the presence of a protein annotated as a βγ-crystallin family protein, named M-crystallin. Solution structure of this protein indicates a typical βγ-crystallin fold with a paired Greek-key motif. Among the known structures of βγ-crystallin members, M-crystallin was found to be structurally similar to the vertebrate lens βγ-crystallins. The Ca<SUP>2+</SUP>-binding properties of this primordial protein are somewhat more similar to those of vertebrate βγ-crystallins than to those of bacterial homologues. These observations, taken together, suggest that amphibian and vertebrate βγ-crystallin domains are evolutionarily more related to archaeal homologues than to bacterial homologues. Additionally, identification of a βγ-crystallin homologue in archaea allows us to demonstrate the presence of this domain in all the three domains of life

A Meta-Analysis of Pedometer-Based Walking Interventions and Weight Loss

PURPOSE Cross-sectional studies show that individuals who walk more tend to be thinner than those who walk less. This does not mean, however, that the association between higher step counts and lower weight is causal or that encouraging sedentary individuals to increase step counts helps them lose weight

Equilibrium unfolding of neuronal calcium sensor-1: N-terminal myristoylation influences unfolding and reduces the protein stiffening in the presence of calcium

Neuronal calcium sensor-1 (NCS-1), a Ca<SUP>2+</SUP>-binding protein of the calcium sensor family, modulates various functions in intracellular signaling pathways. The N-terminal glycine in this protein is myristoylated, which is presumably necessary for its physiological functions. In order to understand the structural role of myristoylation and calcium on conformational stability, we have investigated the equilibrium unfolding and refolding of myristoylated and non-myristoylated NCS-1. The unfolding of these two forms of NCS-1 in the presence of calcium is best characterized by a five-state equilibrium model, and multiple intermediates accumulate during unfolding. Calcium exerts an extrinsic stabilizing effect on both forms of the protein. In the absence of calcium, the stability of both forms is dramatically decreased, and the unfolding follows a four-state equilibrium model. The equilibrium transitions are fully reversible in the presence of calcium. Myristoylation affects the pattern of equilibrium transitions substantially but not the number of intermediates, suggesting a structural role. Our data suggest that myristoylation reduces the stiffening of the protein during initial unfolding in the presence of calcium. The effects of myristoylation are more pronounced when calcium is present, suggesting a relationship between them. Inactivating the third EF-hand motif (E120Q mutant) drastically affects the equilibrium unfolding transitions, and calcium has no effect on these transitions of the mutants. The unfolding transitions of both forms of the mutant are similar to the transitions followed by the apo forms of myristoylated and non-myristoylated NCS-1. These results suggest that the role of myristoylation in unfolding/refolding of the protein is largely dependent on the presence of calcium