Yes, the Russian constitution prevents deportation and extradition of Russian citizens from Russia.
This protection can be found in Chapter 2, Article 61 of the Russian constitution:
> Article 61
>
> 1. A citizen of the Russian Federation may not be deported from Russia or extradited to another State.
>
> 2. The Russian Federation shall guarantee its citizens protection and patronage abroad.
>
>
Several other sources(1, 2, 3) give the same translation for that article, so the translations is probably accurate.
That article, plus the fact that the US and Russia have no extradition treaties, means it's pretty definite that Russian citizens are entirely protected from being extradited from Russia.