Question

2. Which of the following and pairs of to porine. 1. 8, 14​

Answer 1

Step-by-step explanation:

Porins are found in the outer membranes of Gram-

negative bacteria, mitochondria and chloroplasts. They

form channels for small hydrophilic molecules that are

in most cases weakly ion-selective, Typical exclusion

limits are around 600 Da [I-3], Porins are quite resis-

tant to denaturation by heat or detergents, They are

trimeric and consist predominantly of fl.pleated sheet

structure as demonstrated spectroscopically [4]. In coa-

trast, all the other structurally known integral mere.

brahe proteins are essentially o~.helical [5-7]. Two.

dimensional crystals of porin have been studied by elec-

tron microscopic methods yielding the general shape of

the molecule [8-13], Also, a number of three-dimen-

sional perth crystals suitable for X-ray diffraction ana-

lysis have been reported [14-17]. The crystal structure

of the porin from Rhodobacter capsulatus is known at

medium resolution [18], Using a related, new crystal

form [19] and the amino acid sequence (E. Schultz, A.

Kreusch, U, Nestel and G.E. Schulz, unpublished

results) the resolution of the structure analysis has now

been extended to 1.8 A. Here, we report the chain fold

of the 301 amino acids and describe the channel,