 The size of a synthesized protein can be measured by the number of amino acids it contains and by its total molecular mass , which is normally reported in units of <unk> ( synonymous with atomic mass units ) , or the derivative unit <unk> ( kDa ) . <unk> proteins are on average <unk> amino acids long and 53 kDa in mass . The largest known proteins are the <unk> , a component of the muscle <unk> , with a molecular mass of almost 3 @,@ 000 kDa and a total length of almost 27 @,@ 000 amino acids . 
