Ligand binding to a hemoprotein lacking the distal histidine. The myoglobin from aplysia limacina (Val(E7)).

• Main Authors: BELLELLI, Andrea, Blackmore RS, Gibson QH
• Other Authors: Bellelli, Andrea, Blackmore, R, Gibson, Qh
• Format: Article in Journal/Newspaper
• Language: English
• Published: AMERICAN SOCIETY BIOCHEMISTRY MOLECULAR BIOLOGY INC, 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 1990
• Subjects: Sperm whale
• Online Access: http://hdl.handle.net/11573/463279; http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=A1990DU27500033&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a; http://www.jbc.org/content/265/23/13595.full.pdf+html; http://www.scopus.com/inward/record.url?eid=2-s2.0-0025079213&partnerID=65&md5=fe9061d661f9555bbb3d90990928e671

The time course of ligand recombination to the myoglobin from Aplysia limacina, which has Val(E7), was measured following photolysis by flashes of 35 ps to 300 ns with a time resolution of 10 ps or 1 ns. CO shows only bimolecular recombination. O2 has a small geminate reaction with a half-time of tens of picoseconds, but no nanosecond geminate reaction. NO has two picosecond relaxations with half-times of 70 ps (15%) and 1 ns (80%) and one nanosecond relaxation with a half-time of 4.6 ns. The bimolecular rates for O2 and NO are the same: 2 x 107 M-1s-1. Methyl and ethyl isonitriles have a geminate reaction with a half-time of 35 ps. Ethyl isonitrile has, in addition, a nanosecond relaxation (25%) with a half-time of 100 ns. t-Butyl isonitrile has four geminate relaxations (10 ps, 35 ps, 1 ns, and 1 μs). Analysis of the results suggests much easier movement of ligand between the heme pocket and the exterior than in sperm whale myoglobin (His(E7)). The reactivity of the heme is little different, placing the effect of the differences from sperm whale myoglobin on the distal side of the heme.