REAGENT or RESOURCE	SOURCE	IDENTIFIER
Antibodies
Goat Anti-Mouse IgG H&L (Alexa Fluor® 488)	Abcam	Cat#ab150113; RRID: AB_2576208
Anti-FCGRT antibody - Extracellular domain	Abcam	Cat#ab193148; RRID: AB_2801386
Anti-CD55 antibody	Abcam	Cat#ab33111; RRID: AB_726605
Anti-CD55 antibody	Abcam	Cat#ab133684; RRID: AB_2801387
Fluorescein-Conjugated Goat anti-Rabbit IgG (H+L)	ZSGB-BIO	Cat#ZF-0311; RRID: AB_2571576
FcRn-Specific Antibody	Proteintech	Cat#16190-1-AP; RRID: AB_2231751
Primary mouse monoclonal antibody against His tag	ZSGB-BIO	Cat#TA-02; RRID: AB_2801388
Goat anti-rabbit IgG/HRP	ZSGB-BIO	Cat#ZB-2301; RRID: AB_2747412
Goat anti-mouse IgG/HRP	ZSGB-BIO	Cat#ZB-2305; RRID: AB_2747415
Anti- β2 m antibody	biorbyt	Cat#orb153541; RRID: AB_2801389
Anti-GAPDH antibody	Santa Cruz	Cat#sc-47724; RRID: AB_627678
Anti-GAPDH antibody	cwbio	Cat#CW0100M; RRID: AB_2801390
Bacterial and Virus Strains
Echo 6-SJZ-366, GENBANK: MH830353	Isolated from patient; Chen et al., 2017	N/A
Echo 1-XZ2005-T48	China CDC	N/A
Echo 3-GS08-072	China CDC	N/A
Echo 4-XZ10-KA66	China CDC	N/A
Echo 6-D’Amori	China CDC	N/A
Echo 7-HN09-524	China CDC	N/A
Echo 9-XZ99-120	China CDC	N/A
Echo 11-SD03-478	China CDC	N/A
Echo 13-2011-XJ-HT-YTH-63	China CDC	N/A
Echo 14-GS09-522F	China CDC	N/A
Echo 16-XJ11-653128012	China CDC	N/A
Echo 25-GS10-142T	China CDC	N/A
Echo 26-2006-X122	China CDC	N/A
Echo 30-YN2016-AB6	China CDC	N/A
Echo 30-Bastinni	China CDC	N/A
EV-B85-XJ2011-3-29	China CDC	N/A
CV-A9-HB10-221	China CDC	N/A
CV-B4-NM07-714	China CDC	N/A
CV-B5-SJZ-097	China CDC	N/A
Chemicals, Peptides, and Recombinant Proteins
DMEM basic	Thermo Fisher Scientific	Cat#C11995500BT
FBS	Invitrogen	Cat#16000044
Lipofectamine 2000	Invitrogen	Cat#11668019
XtremeGENE HP DNA transfection reagent	Roche	Cat#06366546001
Sucrose	Sigma	Cat#V900116-500 g
Fixation/Permeabilization Solution Kit	BD	Cat#554722
Human protein CD26	Lu et al., 2013	N/A
Human FcRn soluble protein, GENBANK: NM_001136019.2 and NM_004048	This paper	N/A
Human CD55 soluble protein GENBANK: NM_000574.3	This paper	N/A
Critical Commercial Assays
HisTrap HP 5 ml column	GE Healthcare	Cat#17524802
Hiload 16/600 Superdex 200 PG column	GE Healthcare	Cat#28989335
Membrane concentrator	Millipore	Cat#UFC9010961
Series S Sensor Chip CM5	GE Healthcare	Cat#29149603
Deposited Data
Cryo-EM Echovirus 6 bound to FcRn (pH 7.4)	This paper	EMDB-9687, PDB: 6ILM
Cryo-EM Echovirus 6 bound to FcRn (pH 5.5)	This paper	EMDB-9686, PDB: 6ILL
Cryo-EM Echovirus 6 full particle (pH7.4)	This paper	EMDB-9690, PDB: 6ILP
Cryo-EM Echovirus 6 empty particle (pH7.4)	This paper	EMDB-9689, PDB: 6ILO
Cryo-EM Echovirus 6 full particle (pH5.5)	This paper	EMDB-9688, PDB: 6ILN
Cryo-EM Echovirus 6 bound to CD55 (pH 7.4)	This paper	EMDB-9685, PDB: 6ILK
Cryo-EM Echovirus 6 bound to CD55 (pH 5.5)	This paper	EMDB-9684, PDB: 6ILJ
Experimental Models: Cell Lines
Human: HEK293T	ATCC	ATCC CRL-3216
Human: rhabdomyosarcoma (RD) cells	ATCC	ATCC CCL-136
Hamster: Chinese hamster ovary (CHO-K1) cells	ATCC	ATCC CCL-61
Hamster: baby hamster kidney (BHK-21) cells	ATCC	ATCC CCL-10
Human: HEK293T FCGRTKO	Edigene	Cat#CL0029124702A
Human: HEK293T B2MKO	Edigene	Cat#CL0049664423A
Human: HEK293T CD55KO	This paper	N/A
Oligonucleotides
Primers: CaslibF: TATCTTGTGGAAAGGACGAAACACC; CaslibR: AATACGGTTATCCACGCGGC	Zhou et al., 2014	N/A
sgRNA sequence: for CD55 KO: GTTCTCTTCTGT AACCTGGA	This paper	N/A
Primers: for CD55 KO detection: CD55_1F: TTTAGGTAGC TGCGAGGTGC, CD55_1R: ATTTCCCCCAAACACCAGA TG; CD55_2F: TGCATCCCTCAAACAGCCTT, CD55_2R: CCCAAACACCAGATGGTTGAAA; CD55_3F: GCAGGA CATTAGTCCAGGGG, CD55_3R: CCCCAAACACCAGA TGGTTGAA	This paper	N/A
Oligonucleotides used for the membrane protein sgRNA library construction	This paper	Table S1
Recombinant DNA
pMD2.G	Laboratory of Didier Trono	Addgene #12259
pCMVR8.74	Laboratory of Didier Trono	Addgene #22036
lentiCas9-Blast	Sanjana et al., 2014	Addgene #52962
pLVX-IRES-ZsGreen1	Clontech	Cat#632187
pLenti-MCS-BSD	Zhou et al., 2014	N/A
pLVX-DsRed-Monomer-N1	Clonetech	Cat#632152
pLVX-IRES-ZsGreen1-FCGRT	This paper	N/A
pLenti-MCS-BSD-B2M	This paper	N/A
pLVX- Monomer-N1-CD55	This paper	N/A
Beta-2 microglobulin cDNA ORF Clone, Human, N-His tag	Sino biological	Cat# HG11976-NH
pCMV3-FCGRT	This paper	N/A
pCMV3-CD55	This paper	N/A
Software and Algorithms
Model-based Analysis of Genomewide CRISPR/Cas9 Knockout (MAGeCK)	Li et al., 2014	https://sourceforge.net/p/mageck/wiki/Home
TIDE	Brinkman et al., 2014	https://tide.nki.nl/
MEGA program (version 5.0)	Tamura et al., 2011	N/A
BIAcore 3000 Evaluation software	GE Healthcare	N/A
Graphpad Prism 6	GraphPad Software	https://www.graphpad.com/scientificsoftware/prism/
Flowjo 7.6.1	FLOWJO	https://www.flowjo.com/solutions/flowjo/downloads
MotionCor2	Zheng et al., 2017	N/A
CTFFIND4	Rohou and Grigorieff, 2015	N/A
EMAN2	Tang et al., 2007	N/A
Relion-2.0	Scheres, 2012	N/A
PyMOL software	DeLano WL PyMOL molecular graphics system	https://pymol.org/2/
Chimera	Pettersen et al., 2004	N/A
Coot	Emsley et al., 2010	https://www2.mrc-lmb.cam.ac.uk/personal/pemsley/coot/
Phenix	Adams et al., 2010	http://www.phenix-online.org/
MolProbity	Chen et al., 2010	N/A
e2boxer.py	Tang et al., 2007	N/A