Linked Life Data

8527937

Source:http://linkedlifedata.com/resource/pubmed/id/8527937

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
4
pubmed:dateCreated
1996-1-30
pubmed:abstractText
A simple protocol was developed to isolate the integral membrane guanylate cyclase from bleached bovine photoreceptor outer segments. Hypotonic and hypertonic washes strip the photoreceptor outer segment membranes of peripheral proteins. The guanylate cyclase activity is solubilized by dodecyl-b-D-maltoside in a low salt concentration buffer. Phosphatidylcholine, glycerol, and dithiothreitol are used to stabilize the activity during chromatography. GTP-affinity chromatography achieves a 250-fold increase in specific activity over that of membranes stripped of peripheral proteins. From 100 retinas, the protocol yields 100-140 mg of purified guanylate cyclase composed of a 115-kDa subunit. The molar ratio of the guanylate cyclase to rhodopsin is estimated to be 1:440. A significant portion of the freshly solubilized enzyme behaves as a monomer with a Stokes radius of 48.7 A, whereas the purified protein forms homooligomers ranging from dimers to tetramers. These properties are similar to those of ANP and guanylin receptors, indicating that the photoreceptor protein shares characteristics of the membrane receptor guanylate cyclase family. For the physiological substrate MgGTP, the Km and Vmax are 1.07 +/- 0.20 mM and 3262 +/- 514 nmol cGMP min-1 mg-1, respectively, generating a turnover rate of approximately 3.9 nmol cGMP s-1 at physiological substrate concentrations. The relatively high Km suggests that in vivo changes in GTP concentration might modulate the rate of cGMP synthesis. These properties indicate that the photoreceptor membrane guanylate cyclase can sustain a rate of cGMP synthesis comparable to the dark-adapted (basal) rate of cGMP degradation by the cGMP phosphodiesterase.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Aug
pubmed:issn
1046-5928
pubmed:author
pubmed:issnType
Print
pubmed:volume
6
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
501-11
pubmed:dateRevised
2008-11-21
pubmed:meshHeading
pubmed:year
1995
pubmed:articleTitle
The bovine photoreceptor outer segment guanylate cyclase: purification, kinetic properties, and molecular size.
pubmed:affiliation
Committee on Neurobiology, University of Chicago, Illinois 60637, USA.
pubmed:publicationType
Journal Article, In Vitro, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't