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At least 1,297 records · Page 72Linked to original sources
PubMed1997

Further analysis of the role of spectrin repeat motifs in alpha-actinin dimer formation.

Protein constructs consisting of repeats 1-4, repeats 1-3 and repeats 2-4 of the rod domain of chicken alpha-actinin were expressed as fusion proteins in Escherichia coli. Based on the evidence of circular dichroism spectra and cooperative thermal unfolding profiles both truncated rod fragments were judged to have assumed the native structural fold. The thermal stabilities were in both cases significantly lower than that of the intact rod (repeats 1-4). Analyses by sedimentation equilibrium and velocity provided further evidence to show that fragment 1-4 is entirely dimeric in the concentration range of these experiments, resembling therefore the rod domain isolated by proteolytic digestion of native alpha-actinin. Fragment 2-4, and probably also 1-3, show concentration-dependent association, with dissociation constants, estimated by sedimentation equilibrium, in the 1-10 microM range. Thus, in confirmation of earlier work, all four repeats are required to generate a maximally stable anti-parallel dimer (Kd approximately 10 pM), suggesting the presence of binding sites in all of them to allow for aligned pairing.

Actinin↗
PubMed2005

Detection of dynamic water molecules in a microcrystalline sample of the SH3 domain of alpha-spectrin by MAS solid-state NMR.

Water molecules are a major determinant of protein stability and are important for understanding protein-protein interactions. We present two experiments which allow to measure first the effective T(2) decay rate of individual amide proton, and second the magnetization build-up rates for a selective transfer from H(2)O to H(N) using spin diffusion as a mixing element. The experiments are demonstrated for a uniformly (2)H, (15)N labeled sample of a microcrystalline SH3 domain in which exchangeable deuterons were back-substituted with protons. In order to evaluate the NMR experimental data, as X-ray structure of the protein was determined using the same crystallization protocol as for the solid-state NMR sample. The NMR experimental data are correlated with the dipolar couplings calculated from H(2)O-H(N) distances which were extracted from the X-ray structure of the protein. We find that the H(N) T(2) decay rates and H(2)O-H(N) build-up rates are sensitive to distance and dynamics of the detected water molecules with respect to the protein. We show that qualitative information about localization and dynamics of internal water molecules can be obtained in the solid-state by interpretation of the spin dynamics of a reporter amide proton.

Amides↗
PubMed1986

Plasma membranes purified from myeloid leukemia cells before and after differentiation. I. Characterization of spectrin-like proteins and increased association of actin.

Two-step sucrose density gradient centrifugation was used to isolate the plasma membrane of a myeloid leukemia cell line (Ml). Calspectin (or fodrin) was identified in the Triton-insoluble fraction from the plasma membrane, and the molecular size and actin- and calmodulin-binding activity were studied. During differentiation of this cell line, which accompanied the induction of cell motility and phagocytic activity, the membrane-bound actin increased dramatically, whereas calspectin increased only slightly. Therefore, calspectin does not appear to have a major function in the increased binding of actin filaments to the plasma membrane, a requirement for the induction of cell motility.

Acid Phosphatase↗