Search PubMed⌕ Search

Biomedical subjects

M Balint

Publications and source records attributed to M Balint.

At least 19 recordsLinked to original sources
PubMed1984

Effect of nucleotides, divalent cations and temperature on the tryptic susceptibility of myosin subfragment 1.

The kinetics of tryptic breakdown of the heavy chain of chymotryptic myosin subfragment 1 (S1) according to the following scheme (where the numbers represent approximate masses in kDa) are altered at 21 degrees C by divalent (Formula: see text) cations (Me2+) and by ATP, ADP, adenosine 5'-[beta, gamma-imino]triphosphate or PPi, with or without Me2+. ATP or its analogs slow step 2 and accelerate steps 3 and 4, while Me2+ accelerates step 2. ATP and its analogs decrease the amount of a transient 27-kDa peptide [Hozumi, T. & Muhlrad, A. (1981) Biochemistry 20, 2945-2950]. We have found direct evidence for the suggestion in this reference that the 27-kDa peptide is not an obligatory precursor of the 25-kDa fragment and that ATP or ADP suppresses the formation of the larger N-terminal fragment rather than accelerates its breakdown. Cross-linking of sulfhydryl groups located in the 20-kDa fragment leads to trapping of MgADP in the N-terminal 25-kDa peptide [Wells, J.A. & Yount, R.G. (1980) Biochemistry 19, 1711-1717]; this process affects the tryptic fragmentation of S1 similarly to, but less effectively than, nucleotides. Acts-S1 formation prevents the effect of ATP on fragmentation. At 37 degrees C S1 loses ATPase activity; tryptic digestion proceeds more rapidly and the 50-kDa and 25-kDa fragments are degraded to small peptides. Nucleotides protect against the effects of higher temperature by producing conformational changes not only in the 27-kDa N-terminal portion (containing the putative nucleotide binding site) of the heavy chain of S1 but also in the 50-kDa peptide.

Actomyosin↗
PubMed1983

The proteolytic substructure of light meromyosin. Localization of a region responsible for the low ionic strength insolubility of myosin.

Light meromyosin (LMM), prepared by limited tryptic digestion of myosin, usually contains several polypeptide chains, LMM-A, LMM-B, and LMM-C in decreasing order of molecular weight estimated from sodium dodecyl sulfate-gel electrophoresis. Further limited tryptic digestion of LMM produces well defined fragments (Balint, M., Szilagyi, L., Fekete, Gy., Blazso, M., and Biro, E. N. A. J. Mol. Biol. (1968) 37, 317-330). Fragments LF-1, LMM-D, LF-2, and LF-3, with chain masses equal to 63, 56, 47, and 30 kDa, respectively, have been isolated by column chromatography. Based on the time course of the changes in the sodium dodecyl sulfate-gel pattern of the digests, chain masses estimated from sodium dodecyl sulfate-gel electrophoresis, and the NH2- and COOH-terminal sequences of the isolated peptides, the following scheme can be deduced. Formula; see text. C and N over the arrows indicate removal of residues from the COOH and NH2 terminus, respectively. The positions of the peptides along the myosin heavy chain have been established by comparison with the published primary structures of rabbit skeletal (Elzinga, M., Behar, K., Walton, G., and Trus, B. L. (1980) Fed. Proc. 33, 1579) and nematode myosin (McLachlan, A. D., and Karn, J. (1982) Nature (Lond.) 299, 226-231). LMM and fragment LMM-D are insoluble, whereas LF-1, LF-2, and LF-3 are soluble at low ionic strength. Their solubility properties, in conjunction with their locations along the myosin heavy chain, suggest that a relatively small stretch of peptide (chain weight, 5,000 Da) located about 100 residues from the COOH terminus of myosin heavy chain is responsible for the insolubility of LMM at low ionic strength.

Animals↗
PubMed1982

Crosslinking by thiol disulfide interchange of 5,5'-dithiobis(2-nitrobenzoic acid)-treated light chain and heavy chain of rabbit skeletal myosin.

Interchain disulfide crosslinks between the heavy-chain fragment in heavy meromyosin and myosin light chain 2, generated by 5,5'-dithiobis(2-nitrobenzoic acid (Nbs2), are formed under appropriate ionic conditions at neutral pH as revealed by liberation of the chromogenic 2-nitro-5-thiobenzoic acid. The presence of the original or of a slightly digested light chain 2 reduces the rate of the reaction of heavy meromyosin with Nbs2-modified light chain 2 by 32 - 39%, if Ca2+ is present. Dodecyl sulfate/polyacrylamide gel electrophoresis in absence of reducing agents shows that Nbs2-modified light chain 2 attaches to the heavy chain in the region of the 21-kDa fragment of heavy meromyosin, which contains the essential thiol groups and which has been located at the subfragment 1/subfragment 2 junction of myosin [Balint, M., Wolf, I., Tarcsafalvi, A., Gergely, J. and Sreter, F. A. (1978) Arch. Biochem. Biophys. 190, 793-799]. Modification of thiol-1 groups with iodoacetamide as well as crosslinking the thiol-1 and thiol-2 groups by the bifunctional reagent p-N,N'-phenylenedimaleimide prior to incubation with Nbs2-modified light chain 2 has no substantial effect on the crosslinking reaction. This indicates that other thiol groups are involved in the binding of Nbs2-modified light chain 2 to the heavy chain. An examination of K+, Ca2+, Mg2+ and actin-activated Mg2+ ATPase activities of heavy meromyosin that had been crosslinked with Nbs2-modified light chain 2 shows only a slight change in comparison with intact heavy meromyosin, indicating that crosslinking had not altered significantly the hydrolytic site. Crosslinking of Nbs2-modified light chain 2 to light-chain-2-deficient heavy meromyosin restored the original light-chain-2-dependent Ca2+ sensitivity of the tryptic fragmentation of heavy meromyosin, suggesting that crosslinking takes place at the proper binding site for light 2.

Animals↗