Above shows a cylinder and arrow representation for the -helices and -strands, r
ID: 89124 • Letter: A
Question
Above shows a cylinder and arrow representation for the -helices and -strands, respectively, of the transmembrane protein rhodopsin. Rhodopsin is found within light-collecting cells in the eye. The interior of the protein houses the photon-collecting prosthetic coenzyme retinal (shown beside rhodopsin).
a) What is the length of the –strand starting at amino acid 185 in Ångstroms? (3 marks) Length = ____________Å
b) At the bottom of the diagram is a box with an arrow pointing to it:
i. What is the secondary structure being highlighted in this box that, yes, is part of the –sheet, but really connects the two strands of the sheet?
ii) This particular secondary structure has two main types. Which type is the one shown in the box?
iii) Identify the other type and state how it is different from this type (be specific).
iv) What non-covalent forces stabilize the secondary structure shown in the box (be specific in naming residues and the interacting atoms on them)?
retinal (shown beside rhodopsin) ooct APAVQSTI Rhodopsin Cytoplasmic SNFR RF FRMT 180E LV GGE FGGR A PA Membrane AT PP STY SF QG s DF LYvoPAE YFvF Extracellular vv GTK AeN.MN Page 7Explanation / Answer
[A]
What is the length of the –strand starting at amino acid 185 in Ångstroms? (3 marks) Length =
the distance between two consecutive residues =3.5Ao
and total 5 residues are present so total length will be 3.5*5=17.5 Ao
[B]
[i] anti parallel beta sheet and YES they connect
[ii] the -hairpin, to link two antiparallel strands by a short loop of 2-5 residues
[iii] the remaining portion beyond the box is parallel extension of beta sheet. The -hairpin differs form -antiparallel as the constituent amino acids in former case the higher degree of freedom and can twisted much as compared to later.
[iv] amino acids shown are
G-Glycine ; F Phenylalanine; P- Proline undergo hydrophobic interaction
N Asparagine (N-atoms as H-bond formation)