This chapter focuses on wheat gluten protein and how its protein components, gliadin and glutenin, interact at the molecular level to produce structures, which contribute to particular functional properties. The aspects of gluten protein are highlighted in wheat gluten, in both, food and non-food products. Factors impacting wheat gluten protein chemistry and structure under various processing conditions and in different end-use products are discussed. The influence of the genetic make-up of wheat grain on the molecular structure and functional performance of gluten protein in the end-use products is discussed. The main factors steering wheat gluten protein structure-function relationships are thus summarised in the context of traditional and innovative applications.