In helical, the protomers (structural unit of an oligomeric protein) are not grouped in capsomeres but are bound to each other forming a ribbon-like structure which folds into a helix.
In structural biology, a protomer is the structural unit of an oligomeric protein. Protomers usually arrange in cyclic symmetry to form closed point group symmetries. A protein complex or multiprotein complex is a group of two or more associated polypeptide chains. Different polypeptide chains may have different functions. A capsid is the protein shell of a virus, enclosing its genetic material. It consists of several oligomeric (repeating) structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or may not correspond to individual proteins, are called capsomeres. The capsomere is a subunit of the capsid, an outer covering of protein that protects the genetic material of a virus. Capsomeres self-assemble to form the capsid. Subunits called protomers aggregate to form capsomeres. A helix (/hilks/), plural helixes or helices (/hlsiz/), is a shape like a corkscrew or spiral staircase. It is the smallest unit composed of at least two different protein chains that form a larger hetero-oligomer by association of two or more copies of this unit. In chemistry and biochemistry, an oligomer (/lmr/ (listen)) is a molecule that consists of a few similar or identical repeating units which could be derived, actually or conceptually, from copies of a smaller molecule, its monomer. The oligomer concept contrasted to that of a polymer which is usually understood to have a large number of units, possibly thousands or millions. However, there is no sharp distinction between these two concepts. This structure folds into a helix because the protomers are thicker at one end than at the other. 
