Studies on the amino groups of myosin ATPase IV. Effect of ATP and its analogs on the spectral properties of trinitrophenylated myosin and its active fragments

Andras Muhlrad*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

22 Scopus citations

Abstract

A considerable blue shift was observed in the absorption spectrum of the trinitrophenyl moiety attached to a functional ε-lysyl amino group of subfragment-1, heavy meromyosin and myosin on addition of ATP or ATP analogs. The resulting difference spectra showed a maximum at 320 and a minimum at 365 nm. The greatest spectral change was observed with a non-hydrolyzable ATP analog, adenosine 5′-(β,γ-imino)triphosphate and it decreased in the order adenosine 5′-(β,γ-imino)triphosphate, ATP and ADP. The ATP-induced difference spectrum changed to that of ADP upon the hydrolysis of ATP. The observed spectra were dependent on temperature and ionic strength. Difference spectra were produced also by ITP, IDP and pyrophosphate while AMP was practically ineffective. Mg2+ also caused small spectral changes which are not identical with those induced by ATP analogs. On the basis of measurements carried out on a model compound, it is assumed that as a consequence of the reaction of ATP with a myosin head, the environment of the functional lysyl residue becomes less polar, i.e. it becomes buried in the hydrophobic core of the molecule. Changes on addition of ATP or its analogs were observed also in the circular dichroic (CD) spectrum of trinitrophenylated subfragment-1, which also points to conformational changes in the vicinity of the functional lysyl residue.

Original languageEnglish
Pages (from-to)154-166
Number of pages13
JournalBBA - Protein Structure
Volume493
Issue number1
DOIs
StatePublished - 22 Jul 1977

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