PubMed Health⌕ Search

PubMed · 8742731

Helical processing using PHOELIX.

Abstract

We describe here a set of procedures and algorithms for helical processing that we refer to as the PHOELIX package. The package was developed to provide a time-efficient and semiautomated method for determining a three-dimensional density map from a specimen with helical symmetry. The procedures which are part of PHOELIX are drawn from the original MRC helical processing suite with extensions principally developed using the SUPRIM image processing package. The package in its current form has been optimized for the processing of actomyosin filaments but has been modified and applied to other helical structures.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

B Carragher, M Whittaker, R A Milligan. Helical processing using PHOELIX.. https://doi.org/10.1006/jsbi.1996.0018

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

Extraction and reconstitution of calponin and consequent contractile ability in permeabilized smooth muscle fibers.

We demonstrate reduction and restoration of contractile ability in response to protein extraction and reconstitution in Triton X-100/glycerol-permeabilized smooth muscle fibers. Through significant reduction in the content of caldesmon (CaD), calponin (CaP), and the 20-kDa regulatory light chain (RLC) of myosin, but not other contractile proteins in "chemically skinned" fibers, we substantially reduced the contractile ability of these fibers, as measured by their ability to generate isometric force and to hydrolyze ATP by actomyosin Mg2+ ATPase. When the protein-depleted fibers were then reconstituted (either with a mixture of purified protein standards of CaD, CaP, and myosin RLC or with a protein extract from the demembranized muscle fibers containing CaD, CaP, and myosin RLC plus several low-molecular-mass proteins), all proteins used for reincorporation returned nearly to control levels, as did isometric force generation and rate of ATP hydrolysis. The fact that the low-molecular-mass proteins do not affect contractility in this model system indicates that our methods for reversible modulation of the content of CaP and CaD may provide a valuable tool for studying the thin-filament-based regulation of contractility.

Actomyosin↗

Function of gastrointestinal smooth muscle: from signaling to contractile proteins.

The action of smooth muscle in the intestinal wall produces tonic contractions that maintain organ dimension against an imposed load such as a bolus of food, as well as forceful contractions that produce muscle shortening to propel the bolus along the gastrointestinal tract. These functions are regulated by intrinsic electrical and mechanical properties of smooth muscle. The complex signaling process that underlies these functions is discussed in this article. We propose a model that describes the facilitation of sustained contraction of smooth muscle cells in the gut.

Actomyosin↗

Different functional properties of troponin T mutants that cause dilated cardiomyopathy.

The effects of Troponin T (TnT) mutants R141W and DeltaK210, the only two currently known mutations in TnT that cause dilated cardiomyopathy(DCM) independent of familial hypertrophic cardiomyopathy (FHC), and TnT-K273E, a mutation that leads to a progression from FHC to DCM, were investigated. Studies on the Ca2+ sensitivity of force development in porcine cardiac fibers demonstrated that TnT-DeltaK210 caused a significant decrease in Ca2+ sensitivity, whereas the TnT-R141W did not result in any change in Ca2+ sensitivity when compared with human cardiac wild-type TnT (HCWTnT). TnT-DeltaK210 also caused a decrease in maximal force when compared with HCWTnT and TnT-R141W. In addition, the TnT-DeltaK210 mutant decreased maximal ATPase activity in the presence of Ca2+. However, the TnT-K273E mutation caused a significant increase in Ca2+ sensitivity but behaved similarly to HCWTnT in actomyosin activation assays. Inhibition of ATPase activity in reconstituted actin-activated myosin ATPase assays was similar for all three TnT mutants and HCWTnT. Additionally, circular dichroism studies suggest that the secondary structure of all three TnT mutants was similar to that of the HCWTnT. These results suggest that a rightward shift in Ca2+ sensitivity is not the only determinant for the phenotype of DCM.

Actomyosin↗