ABSTRACT
The surface accessibility of mobile domains of rabbit fast muscle myosin subfragment-1 isoenzymes (subfragment-1(A1), (A2)) influenced by interaction with actin has been investigated by proton magnetic resonance spectroscopy using the soluble paramagnetic reagents Cr(CN)6(3-), Fe(CN)6(3-), Mn2+ and the Gd3+ salt of 1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraacetic acid as probes. Anionic probes interact principally with lysine residues disposed close to other non-charged sidechains in both isoenzymes. Additional resonances in subfragment-1(A1) not present in subfragment-1(A2) are also observed to be affected, notably the sharp signal at 3.23 ppm which derives from a -N+ (CH3)3 group found in the N-terminal segment of the A1 light chain, showing that this domain of interaction with actin (Prince et al. (1981) Eur. J. Biochem. 121, 213-219) is situated at a surface location. Different probes identify a heterogeneity in the location and function of mobile sidechains. These results suggest a configurational lability in the various parts of the myosin head, differentially constrained upon interaction with actin and consistent with a structure composed of relatively rigid domains linked by more flexible regions.
Subject(s)
Actins/metabolism , Myosins/metabolism , Amino Acids/analysis , Animals , Binding Sites , Indicators and Reagents , Magnetic Resonance Spectroscopy , Muscles/metabolism , Myosin Subfragments , Peptide Fragments/metabolism , Protein Binding , RabbitsSubject(s)
Calcium-Transporting ATPases , Isoenzymes , Myosins/analysis , Peptide Fragments/analysis , Actins/metabolism , Animals , Calcium-Transporting ATPases/metabolism , Chemical Phenomena , Chemistry , Isoenzymes/metabolism , Magnetic Resonance Spectroscopy , Myosin Subfragments , Myosins/metabolism , Peptide Fragments/metabolism , RabbitsSubject(s)
Hot Temperature/adverse effects , Morbidity , Mortality , Adult , Age Factors , Aged , Climate , England , Female , Humans , Humidity , Male , Middle Aged , Sex FactorsSubject(s)
Thyroid Diseases/diagnosis , Thyroxine-Binding Proteins/analysis , Thyroxine/blood , Female , Humans , Hyperthyroidism/blood , Hyperthyroidism/diagnosis , Male , Myxedema/blood , Myxedema/diagnosis , Pregnancy , Thyroid Function Tests , Thyroid Gland/metabolism , Triiodothyronine/metabolismSubject(s)
Liver/metabolism , Thyroxine/analogs & derivatives , Thyroxine/metabolism , Animals , Binding Sites , Perfusion , RatsABSTRACT
The effects of surgical stress on the metabolism of the retinol-binding-protein-thyroxine-binding-prealbumin complex were investigated. The immediate postsurgical period was characterized by a rapid decline in the serum concentration of retinol, retinol binding protein and triiodothyronine and an increase in the 24 h urinary excretion of retinol, retinol-binding-protein and thyroxine. Similar, but less pronounced, changes were seen in other subjects suffering acute myocardial infarction but were not observed in normal healthy euthyroid males or in pre-operative euthyroid patients. The preparation of specific anti-retinol binding protein anti-serum and the use of this in 'monorocket' immunoelectrophoresis are also described.
Subject(s)
Prealbumin/metabolism , Retinol-Binding Proteins/metabolism , Serum Albumin/metabolism , Stress, Physiological/metabolism , Thyroxine-Binding Proteins/metabolism , Vitamin A/metabolism , Antibodies/analysis , Humans , Myocardial Infarction/metabolism , Retinol-Binding Proteins/immunology , Retinol-Binding Proteins/urine , Thyroxine/urine , Triiodothyronine/blood , Vitamin A/urineABSTRACT
A theoretical model is proposed which describes the binding of thyroid hormones to serum proteins in terms of easily determined parameters, Not only free hormone concentration but also the distribution of hormone among various binding sites may be computed. The mathematical approach is capable of dealing with models of differing complexity of binding from simple 'one binding site per protein molecule' systems to those involving 'negative co-operativity'. The approach gives predictions of thyroid function parameters which are in good agreement with those observed in practice.
