  Recent measurements of the $W$-boson charge asymmetry and of the $Z$-boson
production cross sections, performed at the Tevatron collider in Run II by the
D0 and CDF collaborations, are studied using the HERAFitter framework to assess
their impact on the proton parton distribution functions (PDFs). The Tevatron
measurements, together with deep-inelastic scattering data from HERA, are
included in a QCD analysis performed at next-to-leading order, and compared to
the predictions obtained using other PDF sets from different groups. Good
agreement between measurements and theoretical predictions is observed. The
Tevatron data provide significant constraints on the $d$-valence quark
distribution.
