Alfa ravan

Alfa ravan (alfa naborana ravan ili polarna naborana ravan) je hipotetička sekundarna struktura proteina, koji su predložili Lajnus Poling i Robert Kori 1951.^[1]^[2]^[3] Patern vodoničnog vezivanja u alfa ravni je sličan sa paternom beta ravni, ali je orijentacija karbonilnih i amino grupa u peptidnim jedinicama osobena; sve karbonilne grupe se orijentisane u istom smeru, i sve amino grupe u suprotnom smeru ravni. Stoga alfa ravan poseduje inherentno razdvajanje elektrostatičkog naelektrisanja, pri čemu jedna ivica ravni izlaže negativno naelektrisane karbonilne grupe, a suprotna ivica pozitivno naelektrisane amino grupe. Za razliku od alfa heliksa i beta ravni, za konfiguraciju alfa ravni nije neophodno da svi aminokiselinski ostaci leže unutar istog regiona diedralnih uglova; umesto toga, alfa ravan sadrži ostatke sa naizmeničnim diedralnim uglovima tradicionalnih desnorukih (α_R) i levorukih (α_L) heliksinih regiona Ramačandranovog prostora.

Mada se alfa ravan veoma retko sreće u prirodnim proteinskim strukturama, postoje spekulacije po kojima ona učestvuje u amiloidnoj bolesti.^[4] Primenom molekulsko dinamičkih simulacija je utvrđeno da je alfa ravan jedna od stabilnih formi amiloidogenih proteina.^[5] Ona je takođe nađena među kristalografskim strukturama dezajniranih peptida.^[4]

Reference

^ L, PAULING; COREY, R. B. (1951). „The pleated sheet, a new layer configuration of polypeptide chains”. Proceedings of the National Academy of Sciences of the United States of America. 37 (5): 251—256. Bibcode:1951PNAS...37..251P. PMC 1063350  . PMID 14834147. doi:10.1073/pnas.37.5.251  .
^ Pauling, Linus; Corey, Robert B. (1951). „The Structure of Feather Rachis Keratin”. Proceedings of the National Academy of Sciences. 37 (5): 256—261. Bibcode:1951PNAS...37..256P. PMC 1063351  . PMID 14834148. doi:10.1073/pnas.37.5.256  .
^ Pauling, L.; Corey, R. B. (1951). „Configurations of Polypeptide Chains with Favored Orientations Around Single Bonds: Two New Pleated Sheets”. Proceedings of the National Academy of Sciences of the United States of America. 37 (11): 729—740. Bibcode:1951PNAS...37..729P. PMC 1063460  . PMID 16578412. doi:10.1073/pnas.37.11.729  .
^ ^а ^б Daggett, Valerie (2006). „α-Sheet: The Toxic Conformer in Amyloid Diseases?”. Accounts of Chemical Research. 39 (9): 594—602. PMID 16981675. doi:10.1021/ar0500719.
^ Armen, Roger S.; Demarco, Mari L.; Alonso, Darwin O. V.; Daggett, Valerie (2004). „Pauling and Corey's α-pleated sheet structure may define the prefibrillar amyloidogenic intermediate in amyloid disease”. Proceedings of the National Academy of Sciences. 101 (32): 11622—11627. Bibcode:2004PNAS..10111622A. PMC 511030  . PMID 15280548. doi:10.1073/pnas.0401781101  .

[Pauling1-1] L, PAULING; COREY, R. B. (1951). „The pleated sheet, a new layer configuration of polypeptide chains”. Proceedings of the National Academy of Sciences of the United States of America. 37 (5): 251—256. Bibcode:1951PNAS...37..251P. PMC 1063350  . PMID 14834147. doi:10.1073/pnas.37.5.251  .

[Pauling2-2] Pauling, Linus; Corey, Robert B. (1951). „The Structure of Feather Rachis Keratin”. Proceedings of the National Academy of Sciences. 37 (5): 256—261. Bibcode:1951PNAS...37..256P. PMC 1063351  . PMID 14834148. doi:10.1073/pnas.37.5.256  .

[Pauling3-3] Pauling, L.; Corey, R. B. (1951). „Configurations of Polypeptide Chains with Favored Orientations Around Single Bonds: Two New Pleated Sheets”. Proceedings of the National Academy of Sciences of the United States of America. 37 (11): 729—740. Bibcode:1951PNAS...37..729P. PMC 1063460  . PMID 16578412. doi:10.1073/pnas.37.11.729  .

[Daggett-4] а ^б Daggett, Valerie (2006). „α-Sheet: The Toxic Conformer in Amyloid Diseases?”. Accounts of Chemical Research. 39 (9): 594—602. PMID 16981675. doi:10.1021/ar0500719.

[Armen-5] Armen, Roger S.; Demarco, Mari L.; Alonso, Darwin O. V.; Daggett, Valerie (2004). „Pauling and Corey's α-pleated sheet structure may define the prefibrillar amyloidogenic intermediate in amyloid disease”. Proceedings of the National Academy of Sciences. 101 (32): 11622—11627. Bibcode:2004PNAS..10111622A. PMC 511030  . PMID 15280548. doi:10.1073/pnas.0401781101  .

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