Table 1. Putative Zn 2 -binding residues... | Rockefeller University Press

Table 1.

Putative Zn²⁺-binding residues in H_V1 from several species

Species	H_V1 name	Acid₁	Acid₂	His₁	His₂	Zn²⁺ potency	Reference
						µM^{^a}
Mus musculus	mH_V1	Glu¹¹⁵	Asp¹¹⁹	His¹³⁶	His¹⁸⁹	1	Takeshita et al., 2014
Homo sapiens	hH_V1	Glu¹¹⁹	Asp¹²³	His¹⁴⁰	His¹⁹³	1	Musset et al., 2010b
Rattus norvegicus	RnH_V1	Glu¹¹⁵	Asp¹¹⁹	His¹³⁸	His¹⁹¹	1	Cherny and DeCoursey, 1999
Helisoma trivolvis	HtH_V1	Glu¹¹⁴	Glu¹¹⁸	His²⁰¹	Val²⁵⁴	10	This study
Nicoletia phytophila	NpH_V1	Glu⁷³	Asp⁷⁷	His⁹²	Asp¹⁴⁵	10	Chaves et al., 2018
Ciona intestinalis	CiH_V1	Glu¹⁶⁷	Asp¹⁷¹	His¹⁸⁸	Glu²⁴³	10	Qiu et al., 2016
Coccolithus pelagicus	CpH_V1	Glu⁸⁰	Asp⁸⁴	His¹⁰⁵	Glu¹⁵⁸	30	Taylor et al., 2011
Strongylocentrotus purpuratus	SpH_V1	Glu⁸⁰	Asp⁸⁴	His¹¹⁴	Glu¹⁶⁷	100	Sakata et al., 2016
Danio rerio	DrH_V1	Glu⁸⁴	Asp⁸⁸	His¹⁰⁵	Asp¹⁵⁸	100	Ratanayotha et al., 2017
Lingulodinium polyedrum^{^b}	LpH_V1	Ser⁵²	Glu⁵⁶	Ala¹⁶¹	Thr²¹⁰-Asn²¹¹	∼100	Rodriguez et al., 2017
Emiliania huxleyi^{^c}	EhH_V1	Glu¹¹⁷	Asp¹²¹	Thr²¹⁰	Gly²⁹⁸	∼500	Taylor et al., 2011
Karlodinium veneficum	kH_V1	Gly⁵⁸	Glu⁶²	Glu¹⁰⁹	Gly¹⁶²	Weak	DeCoursey, 2012

Species	H_V1 name	Acid₁	Acid₂	His₁	His₂	Zn²⁺ potency	Reference
						µM^{^a}
Mus musculus	mH_V1	Glu¹¹⁵	Asp¹¹⁹	His¹³⁶	His¹⁸⁹	1	Takeshita et al., 2014
Homo sapiens	hH_V1	Glu¹¹⁹	Asp¹²³	His¹⁴⁰	His¹⁹³	1	Musset et al., 2010b
Rattus norvegicus	RnH_V1	Glu¹¹⁵	Asp¹¹⁹	His¹³⁸	His¹⁹¹	1	Cherny and DeCoursey, 1999
Helisoma trivolvis	HtH_V1	Glu¹¹⁴	Glu¹¹⁸	His²⁰¹	Val²⁵⁴	10	This study
Nicoletia phytophila	NpH_V1	Glu⁷³	Asp⁷⁷	His⁹²	Asp¹⁴⁵	10	Chaves et al., 2018
Ciona intestinalis	CiH_V1	Glu¹⁶⁷	Asp¹⁷¹	His¹⁸⁸	Glu²⁴³	10	Qiu et al., 2016
Coccolithus pelagicus	CpH_V1	Glu⁸⁰	Asp⁸⁴	His¹⁰⁵	Glu¹⁵⁸	30	Taylor et al., 2011
Strongylocentrotus purpuratus	SpH_V1	Glu⁸⁰	Asp⁸⁴	His¹¹⁴	Glu¹⁶⁷	100	Sakata et al., 2016
Danio rerio	DrH_V1	Glu⁸⁴	Asp⁸⁸	His¹⁰⁵	Asp¹⁵⁸	100	Ratanayotha et al., 2017
Lingulodinium polyedrum^{^b}	LpH_V1	Ser⁵²	Glu⁵⁶	Ala¹⁶¹	Thr²¹⁰-Asn²¹¹	∼100	Rodriguez et al., 2017
Emiliania huxleyi^{^c}	EhH_V1	Glu¹¹⁷	Asp¹²¹	Thr²¹⁰	Gly²⁹⁸	∼500	Taylor et al., 2011
Karlodinium veneficum	kH_V1	Gly⁵⁸	Glu⁶²	Glu¹⁰⁹	Gly¹⁶²	Weak	DeCoursey, 2012

Acidic amino acids, red; His, aqua; and neutral residues, gray.

Zn²⁺ potency is defined very approximately as the concentration required to shift the g_H-V relationship by 20 mV or reduce current during a test pulse by 50%. The latter is highly arbitrary and depends strongly on the test voltage used (DeCoursey et al., 2001), but in some cases is the only information available. The four amino acids implicated in Zn²⁺ binding were identified in the crystal structure of mH_V1, which actually included a bound Zn²⁺ atom, confirmed by mutation of each individually (Takeshita et al., 2014). The importance of the two His in hH_V1 have been confirmed in mutation studies (Ramsey et al., 2006; Musset et al., 2010b); all other amino acids in this table are simply located at analogous positions as assessed by multiple alignment.

Given the moderate Zn²⁺ sensitivity of LpH_V1, which lacks three of four coordinating groups, it is quite possible that Zn²⁺ binds at a different location.

EhH_V1 has two alternatively located His in the S1–S2 linker that bind Zn²⁺ (Taylor et al., 2011).

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