Linked Life Data

15734325

Source:http://linkedlifedata.com/resource/pubmed/id/15734325

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
3
pubmed:dateCreated
2005-2-28
pubmed:abstractText
Sialic acid synthase (NeuB) encoded by the neuB gene catalyzes the condensation of N-acetylmannosamine and phospho(enol)pyruvate to form N-acetylneuraminic acid. The enzyme is essential for the biosynthesis of polysialic acid, a capsular sugar polymer functioning as a virulent factor and antiphagocytic barrier. This report demonstrates the first characterization on the quaternary structure of NeuB from Escherichia coli (EcNeuB) and Streptococcus agalactiae (SaNeuB) by nanoflow electrospray ionization mass spectrometry (ESI-MS). Under non-denaturing conditions, Tris buffer was observed to induce a higher ratio of tetramer/dimer of NeuB in the ESI mass spectra, providing supportive evidence for the existence of a "structurally-specific" tetramer. The instrument parameters were found to significantly affect the ratio of detected tetramer/dimer in ESI mass spectra. The harshest conditions, including high desolvation voltages and pressure in the collision cell, led to enhanced detection of the 160 kDa tetramer. The prevalence of dimeric form is likely the cause in loss of tetramer stability in gas-phase arising from insufficient collisional cooling, which implies an asymmetric assembly, possibly composed of dimeric dimers. Most interestingly, the hypothesis was further supported by chemical cross-linking of SaNeuB, in which the reaction of shorter linker yielded mainly the dimer whereas that of longer linker produced both dimer and tetramer. Furthermore, the ESI-MS analysis can reflect dramatic change of pH-dependent quaternary structure in association with enzyme activity, suggesting the tetrameric form may be the primary species responsible for the enzyme catalysis.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Mar
pubmed:issn
1044-0305
pubmed:author
pubmed:issnType
Print
pubmed:volume
16
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
324-32
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
2005
pubmed:articleTitle
Structural characterization of sialic acid synthase by electrospray mass spectrometry--a tetrameric enzyme composed of dimeric dimers.
pubmed:affiliation
Institute of Chemistry, Academia Sinica, Taipei 11529, Taiwan. yjchen@chm.sinica.edu.tw
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't