Born in a peasant family in Rybtsy (now part of Poltava in Ukraine), Muranov moved to Kharkiv in 1900 and worked as a railroad worker.

Muranov was the only Bolshevik deputy (the other one, Roman Malinovsky, was later exposed as a secret police agent) who voted to break away from the rival Menshevik faction of the RSDLP on 15 December 1912.

Facing the death penalty, some Bolshevik deputies and Lev Kamenev, who had been sent to Russia to direct their work in January 1914, wavered and moderated their position.

After the overthrow of the Romanov dynasty by the February Revolution of 1917, Muranov returned to the capital, Petrograd, with other Bolshevik exiles including Lev Kamenev and Joseph Stalin.

Once in control, they advocated conditional support of the newly formed liberal Russian Provisional Government "insofar as it struggles against reaction or counter-revolution".

When Lenin and Grigory Zinoviev returned to Russia on 3 April, they opposed the Kamenev–Stalin–Muranov line and called for a socialist revolution and a complete break with the Mensheviks instead.

[3] Muranov participated in the Bolshevik seizure of power during the October Revolution of 1917 and was elected to the Bolshevik-dominated Presidium of the All-Russian Central Executive Committee at the Second Congress of Soviets.