Sandbox Reserved 191: Difference between revisions

Various mutations have been found in INCL patients<ref name="Ryan-1">PMID:10191107</ref> . Most of these mutations are caused by nonsense or missense mutations within close proximity to the catalytic triad. These mutations lead to an inactive PPT-1 enzyme as they are predicted to create unfavorable steric, polar, and electrostatic interactions that could disturb the nucleophilic elbow. The nucleophilic elbow is responsible for proper location and orientation of the Ser-115. Catalytic ability would be greatly reduced if the original position of Ser-115 was altered because it must be properly orientated to be activated by His-289 in order to attack the substrate. An example of a JNCL mutation such as <scene name='58/580837/Methionine/6'>Val181Met</scene> and <scene name='58/580837/Lysine_mutation/3'>Glu184Lys</scene> gives a good depiction of how the increase in size in the mutated amino acids and positive charge on lysine mutation would create steric and polar clashes with the adjacent helices of the binding pocket compared to the <scene name='58/580837/Val181glu184/2'>Normal Val-181 & Glu-184</scene>  <scene name='58/580837/Arginine_fine/4'>Normal Arg-122</scene> which is described in more detail below.  

LINCl is caused by a mutation in the CLN2 gene which “codes for a lysosomal pepstatin-insensitive acid protease that is deficient in LINCL patients”<ref name="Ryan-2">PMID:9989590</ref> . Mutations that tend to lead to LINCL still disrupt the active site and binding pocket geometry, but not to the degree that is seen in INCL. One LINCL mutation is <scene name='58/580837/Multiple_mutations_mutating/4'>Gln177Glu</scene>.  <scene name='58/580837/Multiple_mutations/4'>Gln-177</scene> acts as a hydrogen bond donor to Ala-171 and Ala-183 and as a hydrogen bond acceptor from Ile-200. The mutation of Gln-177 likely causes a conformation change of the helices in the area. Ala-171 and Ala-183 make hydrophobic contact with the palmitate, and so the altered conformation associated with those two amino acids would decrease binding affinity of the palmitate, decreasing, but not killing the catalytic activity of PPT-1.  

===Mutations leading to Juvinile Neuronal Ceroid Lipofuscinosis===

JNCL is caused by a mutation in the CLN3 gene which codes for a lysosomal membrane protein of unknown function <ref name="Ryan-3">PMID:9151311</ref>. Unlike the mutations that cause INCL and LINCL, mutations that lead to JNCL are located away from the active site and are seen to cause less damage to the overall structure of PPT-1. Some of the mutations in JNCL have been noted as retaining a low level of PPT-1 activity as the catalytic site is left fairly unperturbed. Mutations associated with JNCl are found in two locations, Thr75Pro with Asp79Gly and <scene name='58/580837/Juvenile_mutation/3'>Tyr247His with Gly250Val</scene>. These mutations are predicted to disturb the geometry of helix α1, increasing the flexibility of the region, and alter the antiparallel βsheet motif in sheets βa and βb compared to the <scene name='58/580837/Tyrosine_normal/1'>Normal Tyr-247 & Gly-250</scene>.

[https://en.wikipedia.org/wiki/Gauche_effect] Wikipedia page on Gauche Effect

[http://en.wikipedia.org/wiki/Palmitic_acid] Wikipedia page on palmitic acid.

[https://en.wikipedia.org/wiki/Infantile_neuronal_ceroid_lipofuscinosis] Wikipedia page on Infantile neuronal ceroid lipofuscinosis

[https://en.wikipedia.org/wiki/PMSF] Wikipedia page on PMSF

[https://en.wikipedia.org/wiki/Protein_chaperones] Wikipedia page on Protein Chaperones

[http://en.wikipedia.org/wiki/Endoplasmic_reticulum]  Wikipedia page on Endoplasmic reticulum

[http://en.wikipedia.org/wiki/Palmitoylation] Wikipedia page on Palmitoylation

[http://www.mun.ca/biology/dmarshall/One%20Pager.htm] Page on Late Infantile neuronal ceroid lipofuscinosis

[http://ghr.nlm.nih.gov/condition/juvenile-batten-disease]  Page on Juvenile neuronal ceroid lipofuscinosis