  We argue that small pitch angle synchrotron emission provides an important
dissipation mechanism which has to be taken into account in the models of
formation of relativistic magnetized gamma-ray burst (GRB) outflows from the
newborn black holes and/or magnetars. We show that if the GRB outflow is proton
loaded, spectral energy distribution of this emission is expected to sharply
peak in 0.1-1~MeV energy band. If the small pitch angle synchrotron emission
efficiently cools relativistic particles of the outflow, its spectrum below the
peak energy is a powerlaw with spectral index alpha ~ -1, close to the typical
spectral index of the time-resolved GRB spectra. Otherwise, the low energy
spectral index can be as hard as alpha ~ 0, as observed at the beginning of the
GRB pulses. We make a conjecture that small pitch angle synchrotron emission
from proton-loaded magnetized GRB outflow could significantly contribute to the
Band component of the prompt emission of GRBs while electromagnetic cascade
initiated by the protons could be responsible for the GeV component.
