Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.3.1 (Mg2+-ATPase)
 1,484 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Limited glutaraldehyde modification of tryptic myosin subfragment 1, which mainly consists of 26-, 50-, and 20-kilodalton (kDa) peptides, resulted in the selective cross-linking of the 20- and 50-kDa peptides. The cross-linking pattern was altered by nucleotides, depending on the base structure. Neither the reactive thiols on the 20-kDa peptide nor the reactive lysyl residue on the 26-kDa peptide was modified with the reagent, regardless of the presence or absence of nucleotide. Glutaraldehyde treatment of the protein resulted in marked increases in its Mg2+-ATPase activity and affinity for actin. High ATPase activity and actin affinity were not produced if the treatment was conducted in the presence of ATP. These ATPase and actin binding properties of the protein derivatives are explained by assuming that glutaraldehyde "freezes" the existing interactions between the 20- and 50-kDa peptides in the activated and nonactivated conformational states, respectively. Taking into account the previous reports that the ATPase site resides between the 26- and 50-kDa peptides, and the 50-kDa peptide binds either ATP or actin, the present results suggest that the 50-kDa peptide acts as a communicating apparatus between the ATPase and actin binding sites of myosin. A simple model for the intersite communication is also proposed.
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PMID:Role of the 50-kilodalton tryptic peptide of myosin subfragment 1 as a communicating apparatus between the adenosinetriphosphatase and actin binding sites. 293 76

Glutaraldehyde (GA) and N-(ethoxycarbonyl)-2-ethoxy-1,2-dihydroquinoline (EEDQ), a hydrophobic, carboxyl group directed, zero-length protein cross-linker, were employed for the chemical cross-linking of the rigor complex between F-actin and the skeletal myosin S-1. The enzymatic properties and structure of the new covalent complexes obtained with both reagents were determined and compared to those known for the EDC-acto-S-1 complex. The GA- or EEDQ-catalyzed covalent attachment of F-actin to the S-1 heavy chain induced an elevated Mg2+-ATPase activity. The turnover rates of the isolated cross-linked complexes were similar to those for EDC-acto-S-1 (30 s-1). The solution stability of the new complexes is also comparable to that exhibited by EDC-acto-S-1. The proteolytic digestion of the isolated AEDANS-labeled covalent complexes and direct cross-linking experiments between actin and various preformed proteolytic S-1 derivatives indicated that, as observed with EDC, the COOH-terminal 20K and the central 50K heavy chain fragments are involved in the cross-linking reactions of GA and EEDQ. KI-depolymerized acto-S-1 complexes cross-linked by EDC, GA, or EEDQ were digested by thrombin which cuts only actin, releasing S-1 heavy chain-actin peptide cross-linked complexes migrating on acrylamide gels with Mr 100K (EDC), 110K and 105K (GA), and 102K (EEDQ); these were fluorescent only when fluorescent S-1 was used. They were identified by immunostaining with specific antibodies directed against selected parts of he NH2-terminal actin segment of residues 1-113.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Cross-linking of the skeletal myosin subfragment 1 heavy chain to the N-terminal actin segment of residues 40-113. 314 Aug 94