Preferential assembly of the tropomyosin heterodimer: equilibrium studies.


Thermal unfolding/refolding studies of the three tropomyosin dimers, alpha alpha, alpha beta, and beta beta, from chicken gizzard muscle were performed to explain the preferential assembly of alpha- and beta-tropomyosin subunits into heterodimers, alpha beta [Lehrer, S. S., & Qian, Y. (1989) J. Biol. Chem. 265, 1134]. Circular dichroism measurements showed that all three dimers unfolded in cooperative reversible transitions with T1/2 = 40.0 degrees C and delta H degrees = 162 kcal/mol for alpha alpha and with T1/2 = 42.6 degrees C and delta H degree = 98 kcal/mol for beta beta at 0.4-0.5 microM concentrations. Fluorescence measurements on pyrenyliodoacetamide-labeled tropomyosin showed that (i) excimer fluorescence decreases in parallel with unfolding of homodimers, (ii) at physiological temperature, heterodimers are formed from micromolar mixtures of homodimers over a period of minutes, and (iii) heterodimers unfold/refold with temperature without appreciable formation of homodimers. To understand the preferential formation of alpha beta, we calculated the concentrations of all species present as a function of temperature for equal total amounts of alpha and beta, using the measured thermodynamic constants of the unfolding/dissociation equilibria for alpha alpha and beta beta. Values for delta H degrees = 225 kcal/mol and T1/2 = 43 degrees C for unfolding of alpha beta at 0.5 microM concentration were obtained from the best fit of the calculations to the measured helical content vs temperature of alpha beta.(ABSTRACT TRUNCATED AT 250 WORDS) Study holds ProTherm entries: 4366, 4367, 4368, 4369, 4370, 4371 Extra Details: additive : EDTA(1 mM),

Submission Details

ID: r4t7dUvK3

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:25 p.m.

Version: 1

Publication Details
Lehrer SS;Stafford WF,Biochemistry (1991) Preferential assembly of the tropomyosin heterodimer: equilibrium studies. PMID:2043610
Additional Information

Structure view and single mutant data analysis

Study data

No weblogo for data of varying length.
Colors: D E R H K S T N Q A V I L M F Y W C G P

Data Distribution

Studies with similar sequences (approximate matches)

Correlation with other assays (exact sequence matches)

Relevant UniProtKB Entries

Percent Identity Matching Chains Protein Accession Entry Name
100.0 Tropomyosin alpha-1 chain Q5KR49 TPM1_BOVIN
100.0 Tropomyosin alpha-1 chain P84335 TPM1_CHEAU
100.0 Tropomyosin alpha-1 chain P04268 TPM1_CHICK
100.0 Tropomyosin alpha-1 chain P58773 TPM1_COTJA
100.0 Tropomyosin alpha-1 chain P13104 TPM1_DANRE
100.0 Tropomyosin alpha-1 chain P09493 TPM1_HUMAN
100.0 Tropomyosin alpha-1 chain P58771 TPM1_MOUSE
100.0 Tropomyosin alpha-1 chain P42639 TPM1_PIG
100.0 Tropomyosin alpha-1 chain P58772 TPM1_RABIT
100.0 Tropomyosin alpha-1 chain P13105 TPM1_RANTE
100.0 Tropomyosin alpha-1 chain P04692 TPM1_RAT
100.0 Tropomyosin alpha-1 chain Q01173 TPM1_XENLA
100.0 Tropomyosin alpha-1 chain Q5KR47 TPM3_BOVIN
100.0 Tropomyosin alpha-1 chain P06753 TPM3_HUMAN
100.0 Tropomyosin alpha-1 chain A1XQV4 TPM3_PIG