Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.31.1 (micrococcal nuclease)
 2,818 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

At the completion of mitosis, the two daughter cells are connected by a channel of membrane-bound cytoplasm, the intercellular bridge. This structure contains parallel arrays of spindle microtubules which are associated, at the bridge midline, with a metallophilic band called the midbody. In an effort to characterize midbody components, intercellular bridges were partially purified. The purification consisted of brief sonication of telophase populations of mouse L929 cells in order to shear intercellular bridges from daughter cells, digestion of chromatin by an excess of micrococcal nuclease, and differential centrifugation to enrich for intercellular bridges. Electron microscopy of these preparations substantiated the identity of the bulk of material as intercellular bridges. After solubilization with sodium dodecyl sulfate, the protein components of these preparations were iodinated with Na(125)I and separated by two-dimensional gel electrophoresis. From these analyses, the major polypeptide components of intercellular bridges appear to be tubulin, varying amounts of plasma membrane proteins, and a polypeptide with an apparent molecular weight of 42,000. Time-course studies reveal that this polypeptide is first detectable in a pelletable form approximately 30 min after cells are released from metaphase block, reaches maximal spot intensity in late telophase, and is no longer detectable in G1 populations. We interpret these data to suggest that the 42,000-dalton polypeptide is a component of the midbody.
 ...
PMID:Partial purification and characterization of the intercellular bridge from cultured mouse cells. 28 7

A crude membrane-bound RNA polymerase, obtained by differential centrifugation of extracts of tomato leaves infected with tobacco mosaic tobamovirus (tomato strain L) TMV-L), was purified by sucrose density gradient centrifugation. Removal of the endogenous RNA template with micrococcal nuclease rendered the polymerase template dependent and template specific. The polymerase was primer independent and able to initiate RNA synthesis on templates containing the 3'-terminal sequences of the TMV-L positive or negative strands. TMV-vulgare RNA was a less efficient template, while RNAs of cucumber mosaic cucumovirus and red clover necrotic mosaic dianthovirus, or 5'-terminal sequences of TMV-L positive or negative strands, did not act as templates for the polymerase. A main product of the reaction with TMV-L genomic RNA as a template, carried out in the presence of [alpha-32P]UTP, was genomic-length single-stranded RNA. This was shown to be the positive strand and uniformly labelled along its length, demonstrating complete replication of TMV-L RNA. Genomic-length double-stranded RNA, labelled in both strands, and small amounts of RNAs corresponding to the single- and double-stranded forms of the coat protein subgenomic mRNA were also formed. Antibodies to N-terminal and C-terminal portions of the 126-kDa protein detected the 126-kDa protein and the 183-kDa readthrough protein in purified RNA polymerase preparations, whereas antibodies to the readthrough portion of the 183-kDa protein detected only the 183-kDa protein. All three antibodies inhibited the template-dependent RNA polymerase, but none of them had any effect on the template-bound enzyme.
 ...
PMID:Complete replication in vitro of tobacco mosaic virus RNA by a template-dependent, membrane-bound RNA polymerase. 870 49

Extracts of vacuole-depleted, tomato mosaic virus (ToMV)-infected plant protoplasts contained an RNA-dependent RNA polymerase (RdRp) that utilized an endogenous template to synthesize ToMV-related positive-strand RNAs in a pattern similar to that observed in vivo. Despite the fact that only minor fractions of the ToMV 130- and 180-kDa replication proteins were associated with membranes, the RdRp activity was exclusively associated with membranes. A genome-sized, negative-strand RNA template was associated with membranes and was resistant to micrococcal nuclease unless treated with detergents. Non-membrane-bound replication proteins did not exhibit RdRp activity, even in the presence of ToMV RNA. While the non-membrane-bound replication proteins remained soluble after treatment with Triton X-100, the same treatment made the membrane-bound replication proteins in a form that precipitated upon low-speed centrifugation. On the other hand, the detergent lysophosphatidylcholine (LPC) efficiently solubilized the membrane-bound replication proteins. Upon LPC treatment, the endogenous template-dependent RdRp activity was reduced and exogenous ToMV RNA template-dependent RdRp activity appeared instead. This activity, as well as the viral 130-kDa protein and the host proteins Hsp70, eukaryotic translation elongation factor 1A (eEF1A), TOM1, and TOM2A copurified with FLAG-tagged viral 180-kDa protein from LPC-solubilized membranes. In contrast, Hsp70 and only small amounts of the 130-kDa protein and eEF1A copurified with FLAG-tagged non-membrane-bound 180-kDa protein. These results suggest that the viral replication proteins are associated with the intracellular membranes harboring TOM1 and TOM2A and that this association is important for RdRp activity. Self-association of the viral replication proteins and their association with other host proteins may also be important for RdRp activity.
 ...
PMID:Membrane-bound tomato mosaic virus replication proteins participate in RNA synthesis and are associated with host proteins in a pattern distinct from those that are not membrane bound. 1691 96