Table 1.

Features of repeat-protein arrays

Type	SS	<nres>	<nrep>/<nrep,gaps>	ΔASApair	ΔASApair,np	ΔASApair,p	ΔASAfold
ARM	ααα	42	5/8	1740±25	1230±22	510±13	2110±48
HEAT	ααα	41	4/13	1670±30	1190±23	480±14	2000±36
TPR1	αα	34	3/5	1125±27	810±20	320±18	1900±38
TPR2	αα	37	3/5	1880±164	1300±101)	580±69	1970±80
ANK	ααβh	33	4/5	1490±19	1010±14	470±8	1510±24
LRR1	β310,βPPII	23	7/10	1675±18	1020±11	650±9	630±11
LRR2	βα	28	7/10	1810±22	1130±18	680±12	900±17
HPR	βββ	18	4/7	1380±18	790±13	580±12	300±9

ARM, armadillo repeat; TPR1 and TPR2, tetratricopeptide repeats of different lengths; ANK, ankyrin repeat; LRR1 and LRR2, leucine-rich repeats of different lengths (and secondary structures); HPR, hexapeptide repeat. SS, secondary structure, where ααα indicates three α-helices per repeat, ααβh indicates two helices followed by a short β-hairpin, β3₁₀ and βPPII. <n_res>, average number of residues per repeat. <n_rep>, median number of repeats per tandem array, based on search results of nonredundant entries in NCBI Genbank using HMMER 2.3.2 ([100]; default settings, E-value less than 10) with hidden markov models (HMMs) from Pfam version 21.0 [101]. <n_rep,gaps>, median number or repeats per tandem array, including each gap 70% or greater the length of a repeating unit as an additional repeat. ΔASA_pair, average amount of solvent-accesible surface area (Ų) buried at the interface, obtained from the average difference in solvent accessible surface [102], between adjacent paired repeats folded in contact and individual repeats. ΔASA_pair,np and ΔASA_pair,p, interfacial nonpolar and polar surface area. ΔASA_fold, the change in surface area on folding of single unpaired repeats, using an extended polypepetide, generated by RIBOSOME (http://roselab.jhu.edu/~raj/Manuals/ribosome.html), as a simple model for the unfolded peptide structure.