Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.64 (proteinase K)
 4,071 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Skeletal muscle actin was lightly digested by proteinase K, which cleaved the peptide bond between Met-47 and Gly-48, producing a C-terminal 35 kDa fragment. Proteinase K-cleaved actin (proK-actin) did not polymerize into F-actin upon addition of salt. In the presence of phalloidin, however, it polymerized slowly into F-actin (proK-F-actin), indicating that the cleaved actin did not dissociate into the individual cleaved fragments but retained the global structure of actin. Electron microscopy showed that proK-F-actin had the typical double-stranded structure of a normal actin filament and formed the arrowhead structure when decorated with HMM. Heavy meromyosin ATPase was weakly activated by proK-F-actin: Vmax = 0.24 s-1, and Kapp = 2.8 microM, while Vmax = 7.6 s-1, and Kapp = 13 microM by F-actin. Correspondingly, in vitro this proK-F-actin slid very slowly on HMM attached to a glass surface at an average velocity of 0.47 microns/s, or 1/12 of that of intact F-actin. The fraction of sliding filaments was less than 50%. Assuming that the nonmotile filaments attached to HMM were not involved in ATPase activation, the sliding velocity correlated with the ATPase activity activated by proK-F-actin.
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PMID:Muscle actin cleaved by proteinase K: its polymerization and in vitro motility. 149 Oct 13

Native tropomyosin activated sliding movement in vitro of F-actin with ATP by 30%. Actin cleaved at the 40-50 loop by subtilisin or proteinase K slid on HMM much slower than intact actin, but native tropomyosin strikingly recovered this defective motility of cleaved actin by 2 to 3 times. On the other hand, with ATP analogues of CTP and ITP, sliding movements of cleaved actin and particularly intact actin were inhibited by native tropomyosin, indicating that native tropomyosin augmented specificity of the myosin substrate of NTP. These results suggested that the 40-50 loop in the small domain 2 of actin interacted directly or indirectly with tropomyosin and play a significant role in cross talk between myosin and native tropomyosin.
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PMID:Restoration of defective mechanochemical properties of cleaved actins by native tropomyosin: involvement of the 40-50 loop in subdomain 2 of actin in interaction with myosin and tropomyosin. 926 42