A structural approach to G-protein signaling mechanisms: Alpha-subunits

Guanin nükletit bağlayıcı proteinler duyusal algılama, protein sentezi, hormonal düzenleme, salgı kesecikleri ve çekirdek taşınımı, hücre büyümesi ve farklılaşmasını da içine alan birçok fizyolojik sürecin düzenlenmesinde rol oynarlar. Bu proteinler (GDP)-bağlı dinlenim durumuyla (GTP)-bağlı aktif durumları arasında bir döngü geçirerek moleküler aracılık görevlerini yerine getirirler. G-proteinleri 3 altbirimden oluşmaktadır: α, β, γ. G-proteininin özgünlüğü α altbirimi tarafından belirlenir. α-altbirimi de iki bölgeden oluşur: GTPaz bölgesi ve α-heliks bölgesi. Aktivasyon GTPaz bölgesindeki anahtar I, II ve III olarak adlandırılan bölgelerde yapısal değişikliklere yol açar. Hem reseptör hem de efektörlerle etkileşimde karboksil ucunun önemli olduğu gösterilmiştir.

G-protein sinyal ileti mekanizmalarına yapısal bir yaklaşım: Alfa altbirimi

Guanine nucleotide binding proteins regulate a variety of physiological processes, including sensual perception, protein synthesis, hormonal regulation, vesicular and nuclear transport, cell growth and differentiation. They act as molecular mediators, cycling between inactive guanosine diphosphate (GDP)-bound and active guanosine triphosphate (GTP)-bound states. G-proteins are composed of three subunits: α, β, γ, where specificity mainly determined by α.The α-subunit consists of two domains: GTPase domain and α-helical domain. Activation results in conformational changes around so called switch I, II and III regions in GTPase- domain. Interaction of the receptor with the carboxyl terminus of α is clearly important. Carboxy terminus is also shown to be important in effector interaction.

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