Protein jelly-roll motif

We have already discussed one envelope protein of influenza virus, neuraminidase, as an example of an up-and-down antiparallel p motif. In the second envelope protein, hemagglutinin, one domain of the polypeptide chain is folded into a jelly roll motif. We shall now look at some other features of hemagglutinin that are important for its biological function. 

FIGURE 12,38. Motifs in protein architecture, (a) Up-and-down barrel, (b) jelly-roll motif, and (c) (/lajg barrel. Compare these with (d), (e), and (f), which is what the folding looks like in three dimensions. 

Jelly-roll motif The folding of a protein in a manner reminiscent of the fold of a jelly roll. 

A number of protein crystal structures has been obtained for this class of enzymes, including those of isopenicillin-N-synthase, " deacetoxycephalosporin C synthase (DAOCS) Figure 14, and clavaminate synthase (CAS) these structures are currently being studied with regards to the effect of structure on the regioselectivity exhibited by these enzymes. For DAOCS the structure shows a jelly-roll motif with the active site situated in a shallow pocket on the edge of... 

Fig. 33. Some motifs in protein structures. The a helix is represented as a coil and 3 sheet as a line with an arrow, (a) helix-tum-helix, (b) Greek key, (c) Jelly roll, and (d) Pap...

Antiparallel p sheets are, as was described earUer, twisted, and they can pack to form a barrel with a hydrophobic core. Three structures are commonly found for -proteins these are the up-and-down barrel (Figure 22a), the Greek key barrel (Figure 22b) and the jelly-roll barrel (Figure 22c). Another motif, shown in Figure 22(d), has been found in pectate lyase [119], even though it was thought too unstable to exist. 

Strand which then returns via two hairpin connections to the strand adjacent to the first. This feature contains a handedness that is only observed in one sense as shown in Fig. 13a. Connection of two of these features gives rise to an eight stranded y3-barrel however, Greek Key motifs are utilized in many ways to form closed structures. An alternative way of forming a closed barrel is found in proteins that exhibit a jelly roll topology (Fig. 13b). This is an abundant motif that is commonly found in virus capsid proteins. 

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