Control of cytoplasmic actin gel-sol transformation by gelsolin, a calcium-dependent regulatory protein.
ABSTRACT The peripheral cytoplasm of macrophages is involved in the control of locomotion, secretion and endocytosis, events common to many eukaryotic cells. During these activities, the cortical cytoplasm, which contains numerous actin filaments1,2, appears to undergo reversible gel-sol transformations3: cycles of gelation and solation are demonstrable in suitably prepared macrophage extracts, and the gels contain tangled actin filaments4. These changes in consistency of cytoplasmic actin may regulate motile events in the macrophage periphery. Calcium in micromolar concentrations prevents gelation of crude macrophage cytoplasmic extracts4, providing a possible link to abundant indirect evidence implicating calcium in the regulation of locomotion, secretion and endocytosis5. Similar calcium-sensitive gelation phenomena occur in crude cell extracts from diverse cell types and may have a relevance for control of cell movements in general6-11. Actin gelation results from the cross-linking of actin filaments (F-actin) by other proteins. In macrophages, a high molecular weight actin-binding protein (ABP) is the principal actin cross-linking protein12. Cross-linking of actin by these purified actin-binding proteins, however, is insensitive to changes in the calcium concentration4,12, so that another factor must mediate the expression of a calcium effect. We have now isolated such a calcium-dependent regulatory protein from macrophages and call it gelsolin.
SourceAvailable from: Ashish Runthala[Show abstract] [Hide abstract]
ABSTRACT: Mutation in a single nucleotide of a gene has the potential to change the structure and/or function of its protein. Albeit simply saying, it is not observed to be a general phenomenon. The effect of mutation is primarily determined by the stereochemical nature of the amino acid which has replaced the previous amino acid, resulting in the residue location being affected. Here we show that despite a change in the frequency of occurrence of a particular amino acid in a particular protein in different types of organisms, the overall function of the protein can still remain unaffected, even when the resultant protein conformation is relatively altered. Phylogenetic trees were constructed for the proteins belonging to the same family on the basis of the sequences extracted from protein structures. Variation in the percentage of every existing amino acid of each of the considered protein is further calculated. In contrast to this sequence based mutual comparison of proteins, structural comparison is also computed in terms of standard TM_Score and alteration in the count of structurally similar residues falling within the 5Å distance deviation. The functional and structural role of an evolutionary alteration or mutation in a protein sequence and its concomitant effect on the protein structure is thus analyzed.Internet Journal of Genomics and Proteomics 12/2014; 1(1):102.
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ABSTRACT: Neurodegeneration has been recognized as the main cause for neuronal diseases. Much effort has been paid to investigate the process of neurodegeneration from the viewpoint of molecular biology. However, the mechanisms of some processes are still unclear. Here we use a new means to study neurodegeneration using atomic force microscopy (AFM) from the aspect of cellular integrity. The morphological information of neuroblastoma cells was obtained by AFM and it showed a great difference in the process of neurodegeneration induced by activation of NMDA receptors.2013 IEEE 7th International Conference on Nano/Molecular Medicine and Engnieering (NANOMED); 11/2013
The Journal of Cell Biology 12/1982; 95(3):711-719. DOI:10.1083/jcb.95.3.711 · 9.69 Impact Factor