ISSN:
1432-2013
Keywords:
Muscle Calcium Troponin C
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract. Two genetically engineered, recombinant versions of native barnacle troponin C (TnC) (BTnC2) were created from the bacterially expressed, recombinant, wild-type BTnC (BTnCWT) to investigate the role of the Ca2+-specific sites in force regulation. The mutant BTnC4– contains a single amino acid mutation in site IV which results in the inactivation of site IV Ca2+ binding; the mutant BTnCTrunc lacks the last 11 amino acids of the C-terminal, and hence most of site IV. Both mutant proteins, which retain an active site II, bind to native TnC-depleted myofibrillar bundles and restore approximately 40% of the tension-generating capacity, about half that seen with purified native BTnC1 or BTnC2. This observation implies that the Mg2+-dependent interaction with troponin I (TnI) is at a location on TnC other than the C-terminal Ca2+-binding sites of BTnC2. Replacement with BTnCTrunc increases the sensitivity of the myofibrillar bundle to changes in ionic strength. Decreasing the ionic strength from 0.15 to 0.075 M increased force by 34%, a value much greater that the 8% increase seen in control bundles or bundles substituted with BTnC4–. These findings implicate TnC in determining this fibre characteristic, although this cannot be simply due to the alteration in the numbers of Ca2+ ions bound by the troponin complex since both BTnC4– and BTnCTrunc bind only 1 mol Ca2+/mol protein
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004249900216
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