Linked Life Data

16787090

Source:http://linkedlifedata.com/resource/pubmed/id/16787090

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
25
pubmed:dateCreated
2006-6-21
pubmed:abstractText
The topology of the bacterial outer-membrane enzyme, PagP, in dodecylphosphocholine micelles was studied by solution NMR using oxygen and water contacts as probes of hydrophobicity and topology. The effects of oxygen on amide protons were measured at an oxygen partial pressure of 20 atm through the paramagnetic contribution to the relaxation rates associated with the decay of two-spin order. A significant gradation of paramagnetic rates was observed for backbone amides belonging to the transmembrane residues. These rates were observed to depend on immersion depth, local hydrophobicity, and steric effects. Variations in the paramagnetic relaxation rates due to local hydrophobicity or steric effects could be, to some extent, averaged out by considering an azimuthally averaged quantity. This averaged paramagnetic rate was found to have a distinct maximum exactly in the middle of the transmembrane domain of PagP, assuming the immersion depth axis is tilted by 25 degrees with respect to the barrel axis. Contact between the protein surface and water was assessed by measuring the amide decay rates during water saturation. The comparison of local contrast effects from both water and oxygen allows one to distinguish among steric effects, local hydrophobicity, and immersion depth. For example, the absence of contrast effects from either water or oxygen at the periplasmic end of beta-strands B and C was consistent with protection effects arising from the association with the N-terminal alpha-helix. A parameter defined by the natural logarithm of the ratio of the normalized paramagnetic relaxation rate to the normalized amide decay rate under water saturation was found to correlate with immersion depth of the corresponding backbone amide nuclei. The results suggest that the oxygen/water contrast experiments give direct information regarding membrane protein topology and surface hydrophobicities, thereby complementing existing NMR structure studies and ESR spin-labeling studies.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jun
pubmed:issn
0002-7863
pubmed:author
pubmed:issnType
Print
pubmed:day
28
pubmed:volume
128
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
8256-64
pubmed:dateRevised
2010-11-18
pubmed:meshHeading
pubmed:year
2006
pubmed:articleTitle
Topology of an outer-membrane enzyme: Measuring oxygen and water contacts in solution NMR studies of PagP.
pubmed:affiliation
Department of Chemistry, University of Toronto, UTM, 3359 Mississauga Road North, Mississauga, Ontario L5L 1C6, Canada.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't