B.A., Emmanuel College 1971
Ph.D., Rutgers University 1976
NYU School of Medicine 1976-1980
Office: Lapham 131C
Membranes form the structural and functional limits of the cell. Membranes separate the cellular contents from the environment and are the site of many essential activities such as energy transduction and the initiation of responses to environmental stimuli. My lab has been studying the molecular events involved in membrane development. We have used two model systems - phototrophic bacteria and methanotrophic bacteria. Unlike most other bacteria, both of these groups form an intracytoplasmic membrane (ICM). In both cases the formation of this membrane is affected by environmental conditions thus allowing laboratory manipulation of membrane formation.
Mutant of R. rubrum lacking the photosynthetic apparatus forming ICM due to the expression of a foreign membrane protein.
Methanotrophic bacteria use methane as a sole source of carbon and energy. The ICM of methanotrophs has a role in the metabolism of one carbon compounds. This is evidenced by the localization of enzymes of methane metabolism to the ICM by immunoelectron microscopy. Formation of the ICM is governed by environmental conditions - specifically copper availability. The first enzyme of methane utilization, methane monooxygenase, is a copper protein.
Phototrophic bacteria, such as Rhodospirillum rubrum, use light as a source of energy. The photosynthetic apparatus is housed in an ICM. Using biochemical, immunochemical, and ultrastructural approaches, work from my laboratory has demonstrated that the ICM and cytoplasmic membrane are continuous and that when triggered by environmental stimuli, the ICM arises from invagination and differentiation of the cytoplasmic membrane. We have provided evidence that the cytoplasmic membrane is differentiated into functional domains. We have cloned the genes encoding the pigment-binding proteins of the photochemical complexes, constructed mutants, and evaluated the effects of these mutations in vivo. Knockout mutants lacking protein components of the photochemical complexes do not form ICM; ICM formation is restored by complementation in trans. These studies demonstrate that the proteins of the photochemical components are required for ICM formation. This suggests that insertion of these proteins in the membrane is a stimulus for membrane proliferation.
Because mutants that lack the pigment-binding proteins do not make ICM but retain the capacity to do so, these mutants have "excess capacity" for the incorporation of membrane proteins. This makes them excellent hosts for the production of heterologous membrane proteins. Current work in the lab involves development of a Rhodospirillum rubrum host/vector system for the production of heterologous membrane proteins.
Collins, M. L. P. Method, vector and system for expressing polypeptides. PCT/US09/30564, patent pending.
Collins, M. L. P. and Y. Cheng. 2004 and 2005. Host/vector system for expression of membrane proteins. U.S. patents 6,680,179 and 6,951,741.
Butzin, N. C., H. A. Owen, and M. L. P. Collins. 2010. A new system for heterologous expression of membrane proteins: Rhodospirillum rubrum. Prot. Exp. Purif. 70: 88-94. Online Reprint
Brantner, C.A., C. C. Remsen, H. A. Owen, L. A.Buchholz, and M. L. P. Collins. 2002. Intracellular localization of the particulate methane monooxygenase and methanol dehydrogenase in Methylomicrobium album BG8. Arch. Microbiol. 178: 59-64. Abstract
Cheng, Y. S., C. A. Brantner, A. Tsapin, and M. L. P. Collins. 2000. Role of the H protein in assembly of the photochemical reaction center and intracytoplasmic membrane in Rhodospirillum rubrum. J. Bacteriol. 182: 1200-1207. Online Reprint
Yuan, H., M. L. P. Collins, and W. E. Antholine. 1997. Low-frequency EPR of the copper in particulate methane monooxygenase from Methylomicrobium albus BG8. J. Amer. Chem Soc. 119: 5073-5074. Online Reprint
Collins, M. L. P., L. A. Buchholz, and C. C. Remsen. 1991. The effect of copper on Methylomonas albus BG8. Appl. Env. Microbiol. 57: 1261-1264. Online Reprint
Hessner, M. H., P. J. Wejksnora, and M. L. P. Collins. 1991. Construction characterization, and complementation of Rhodospirillum rubrum puf region mutants. J. Bacteriol. 173: 5712-5722. Online Reprint