Journal article
Lac permease of Escherichia coli: arginine-302 as a component of the postulated proton relay
Biochemistry (Easton), Vol.26(21), pp.6638-6644
10/01/1987
DOI: 10.1021/bi00395a012
PMID: 2827732
Abstract
The lac permease of Escherichia coli was modified by site-directed mutagenesis such that Arg-302 in putative helix IX was replaced with Leu. In addition, Ser-300 (helix IX) was replaced with Ala, and Lys-319 in putative helix X was replaced with Leu. Permease with Leu at position 302 manifests properties that are similar to those of permease with Arg in place of His-322 [Püttner, I. B., Sarkar, H. K., Poonian, M. S., & Kaback, H. R. (1986) Biochemistry 25, 4483]. Thus, permease with Leu-302 is markedly defective in active lactose transport, efflux, exchange, and counterflow but catalyzes downhill influx of lactose at high substrate concentrations without H+ translocation. In contrast, permease molecules with Ala at position 300 or Leu at position 319 catalyze lactose/H+ symport in a manner indistinguishable from that of wild-type permease. By molecular modeling, Arg-302 may be positioned in helix IX so that it faces the postulated His-322/Glu-325 ion pair in helix X. In this manner, the guanidino group in Arg-302 may interact with the imidazole of His-322 and thereby play a role in the H+ relay suggested to be involved in lactose/H+ symport [Carrasco, N., Antes, L. M., Poonian, M. S., & Kaback, H. R. (1986) Biochemistry 25, 4486].
Details
- Title: Subtitle
- Lac permease of Escherichia coli: arginine-302 as a component of the postulated proton relay
- Creators
- Donald R MenickNancy CarrascoLisa AntesLekha PatelH. Ronald Kaback
- Resource Type
- Journal article
- Publication Details
- Biochemistry (Easton), Vol.26(21), pp.6638-6644
- Publisher
- American Chemical Society
- DOI
- 10.1021/bi00395a012
- PMID
- 2827732
- ISSN
- 0006-2960
- eISSN
- 1520-4995
- Language
- English
- Date published
- 10/01/1987
- Academic Unit
- Nephrology; Internal Medicine
- Record Identifier
- 9984094768502771
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