TABLE 4.
Allelic variations in 31 GAS isolates
| emm sequencea | No. of isolates with variations/ total no.b | Amino acid variation(s)c |
|---|---|---|
| emm1 | 10/15 | D77N |
| emm1.16 | 1/15 | N29T |
| emm1.17 | 1/15 | D31S |
| emm1.2.b | 1/1 | K40E |
| emm14.3 | 1/1 | G18D + E22K + K23N + A25G + V35T + A65V + T81Ad |
| emm39.1 | 1/1 | I9R + E10Q + E11K + K14E + Q31E + G45E + K52E + N53K + V54L + K67E |
| emm53 | 1/5 | D87E + N110D |
| emm58.4 | 1/11 | D20G |
| emm58.5 | 4/11 | L10F + T42A |
| emm64.3 | 1/1 | R2K + G6R + A9D + N16S + R29K + K38E + D45G + N55K + N57K + K61E + K62N + N64K + E66D + V78D + V83A + E86N + D117N |
| emm71 | 1/1 | A57T |
| emm74 | 1/1 | E67K |
| emm75.1 | 1/2 | R31K |
| emm77 | 1/3 | S112I |
| emm93.1 | 1/1 | Y10H + G29D + N39D + K73R |
| emm101 | 1/2 | One in-frame deletion of 13 residues (ELERLKNERHDHD) from positions 80 to 92 |
| emm102 | 1/2 | L67H + L83Q + L94Q |
| emm102 | 1/2 | T102A |
| emm103 | 1/2 | In-frame insertion of 7 residues (QEERQKN) between positions 102 and 103 |
Alleles (indicated by numeral following decimal point) are based on changes in the predicted hypervariable N-terminal 50 residues of the processed M proteins compared to CDC reference sequences for the products of emm1, emm1.2, emm14, emm39, emm58, emm64, emm75, and emm93. Alleles emm14.3 and emm75.1, which have been seen within the United States, were in the CDC database prior to this study (from pharyngeal and invasive isolates, respectively). Other alterations outside of this 50-residue segment are also indicated.
Total number of isolates with the corresponding emm type. Except for emm53, emm58, and emm75 isolates, all isolates with the indicated emm type were sequenced. A total of 4 of 5 emm53 isolates, 10 of 11 emm58 isolates, and 1 of 2 emm75 isolates were sequenced.
The number indicates the position of the amino acid in the mature protein. All strains with allelic variations were sequenced two or three times.
The amino acid sequences of the emm14.3 product and the product of emm14 (reference sequence) diverge significantly after mature protein residue 93. However, this region of the Hong Kong emm14.3 sequence has complete homology to the corresponding region (mature protein residue 101) of the reference emm14.3 sequence in the CDC database.