6CSL:
reference: Structural characterisation of the HT3 motif of the polyhistidine triad protein D from Streptococcus pneumoniae., Luo Z, Pederick VG, Paton JC, McDevitt CA, Kobe B, FEBS Lett. 2018 Jun 1. doi: 10.1002/1873-3468.13122. PMID: 29856892

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