(a) Alignment of the NP C-termini from Ebola virus genomes available in GenBank grouped according to species and then the chronological order. The key to abbreviations of viruses is as follows: Z, EBOV; S, SUDV; Bun, BDBV; TF, TAFV; Bom, Bombali; R, RESTV. Genbank accession number of the sequences used: Z Mayinga DRC 1976, JQ352763.1; Z Bonduni DRC 1977, KC242791.1; Z Gabon 1994, Y09358.1; Z Kikwit DRC 1995, AF054908.1; Z Eko Gabon 1996, KC242793.1; Z Ikot Gabon 1996, KC242798.1; Z Ilembe Gabon 2002, KC242800.1; Z Kelle2 RC 2003, KF113529.1; Z Luebo DRC 2007, HQ613403; Z Luebo DRC 2008, HQ613402; Z Boende-Lokolia DRC 2014, KM519951.1; Z Makona, Guinea 2014, KJ660346.2; Z Makona Sierra Leone 2014, KM034550; Z Makona Liberia 2014, KP178538; Z Likati DRC 2017, MH481611; Z Ituri-Ben230 DRC 2018, MK163663.1; Z Tumba DRC 2018, MH733478; Bun Uganda 2007, NC_014373.1; Bun #14 DRC 2012, KC545396.1; TF IC-1 1994, NC_014372; Bom M Sierra Leone 2016, NC_039345; Bom C Sierra Leone 2016, MF319186; S Boniface Sudan 1976, AF173836.1; S Maleo Sudan 1979, KC242783.2; S Gulu Uganda 2000, Y729654.1; S Yambio Sudan 2004, EU338380.1; S Nakisamata Uganda 2011, JN638998.1; S 682 Uganda 2012, KC545392.1; R Reston 1989/1990, AB050936.1; R PUM Reston 1989/1990, #AY769362; R Penn 1989/1990, AF522874; R Italy 1992, KY798007.1; R Alice 1996, JX477166.1; R Phl Sw-A 2008, FJ621583.1; R Phl Sw-E 2008, FJ621585.1; R Phl 2015, MF540570.1. (b) Schematic of the NP C-terminus secondary structure with interface residues from each of the complexes shown as yellow ovals except for the sdAb SB chains A–B interface colored moss green. The 2:2 tetramers of sdAb SB + SUDV NP610 and sdAb SB + SUDV NP634 each have four interfaces of two distinct types; chain A is one of the sdAbs, while chains D and B are two different NPs. NP, nucleoprotein; sdAb, single-domain antibody; EBOV, Zaire ebolavirus; SUDV, Sudan ebolavirus; BDBV, Bundibugyo ebolavirus; TAFV, Taï Forest ebolavirus;RESTV, Reston ebolavirus.