Import of cytochrome c into mitochondria

The covalent attachment of heme to apocytochrome c, and therefore the import of cytochrome c into mitochondria, is dependent on both NADH plus a cytosolic cofactor that has been identified to be FMN or FAD. NADH in concert with flavin nucleotides mediates the reduction of heme. Heme in the reduced state is a prerequisite for its covalent attachment to apocytochrome c by the enzyme cytochrome c heme lyase and thus for subsequent translocation of cytochrome c across the outer mitochondrial membrane during import

Information needs and institutional development

Michael W. Nicholson; Armine R. Mirzoya

Privacy and Accountability in Black-Box Medicine

Black-box medicine—the use of big data and sophisticated machine learning techniques for health-care applications—could be the future of personalized medicine. Black-box medicine promises to make it easier to diagnose rare diseases and conditions, identify the most promising treatments, and allocate scarce resources among different patients. But to succeed, it must overcome two separate, but related, problems: patient privacy and algorithmic accountability. Privacy is a problem because researchers need access to huge amounts of patient health information to generate useful medical predictions. And accountability is a problem because black-box algorithms must be verified by outsiders to ensure they are accurate and unbiased, but this means giving outsiders access to this health information. This article examines the tension between the twin goals of privacy and accountability and develops a framework for balancing that tension. It proposes three pillars for an effective system of privacy-preserving accountability: substantive limitations on the collection, use, and disclosure of patient information; independent gatekeepers regulating information sharing between those developing and verifying black-box algorithms; and information-security requirements to prevent unintentional disclosures of patient information. The article examines and draws on a similar debate in the field of clinical trials, where disclosing information from past trials can lead to new treatments but also threatens patient privacy

Manufacturing Barriers to Biologics Competition and Innovation

As finding breakthrough small-molecule drugs gets harder, drug companies are increasingly turning to “large molecule” biologics. Although biologics represent many of the most promising new therapies for previously intractable diseases, they are extremely expensive. Moreover, the pathway for generic-type competition set up by Congress in 2010 is unlikely to yield significant cost savings. In this Article, we provide a fresh diagnosis of, and prescription for, this major public policy problem. We argue that the key cause is pervasive trade secrecy in the complex area of biologics manufacturing. Under the current regime, this trade secrecy, combined with certain features of FDA regulation, not only creates high barriers to entry of indefinite duration but also undermines efforts to advance fundamental knowledge. In sharp contrast, offering incentives for information disclosure to originator manufacturers would leverage the existing interaction of trade secrecy and the regulatory state in a positive direction. Although trade secrecy, particularly in complex areas like biologics manufacturing, often involves tacit knowledge that is difficult to codify and thus transfer, in this case regulatory requirements that originator manufacturers submit manufacturing details have already codified the relevant tacit knowledge. Incentivizing disclosure of these regulatory submissions would not only spur competition but it would provide a rich source of information upon which additional research, including fundamental research into the science of manufacturing, could build. In addition to provide fresh diagnosis and prescription in the specific area of biologics, the Article contributes to more general scholarship on trade secrecy and tacit knowledge. Prior scholarship has neglected the extent to which regulation can turn tacit knowledge not only into codified knowledge but into precisely the type of codified knowledge that is most likely to be useful and accurate. The Article also draws a link to the literature on adaptive regulation, arguing that greater regulatory flexibility is necessary and that more fundamental knowledge should spur flexibility. A vastly shortened version of the central argument that manufacturing trade secrecy hampers biosimilar development was published at 348 Science 188 (2015), available online

Nudging the FDA

[Excerpt] The FDA’s regulation of drugs is frequently the subject of policy debate, with arguments falling into two camps. On the one hand, a libertarian view of patients and the health care system holds high the value of consumer choice. Patients should get all the information and the drugs they want; the FDA should do what it can to enforce some basic standards but should otherwise get out of the way. On the other hand, a paternalist view values the FDA’s role as an expert agency standing between patients and a set of potentially dangerous drugs and potentially unscrupulous or at least insufficiently careful drug companies. We lay out here some of the ways the FDA regulates drugs, including some normally left out of the debate, and suggest a middle ground between libertarian and paternalistic approaches focused on correcting information asymmetry and aligning incentives.

Role of cytochrome c heme lyase in the import of cytochrome c into mitochondria

The import of cytochrome c into Neurospora crassa mitochondria was examined at distinct stages in vitro. The precursor protein, apocytochrome c, binds to mitochondria with high affinity and specificity but is not transported completely across the outer membrane in the absence of conversion to holocytochrome c. The bound apocytochrome c is accessible to externally added proteases but at the same time penetrates far enough through the outer membrane to interact with cytochrome c heme lyase. Formation of a complex in which apocytochrome c and cytochrome c heme lyase participate represents the rate-limiting step of cytochrome c import. Conversion from the bound state to holocytochrome c, on the other hand, occurs 10-30-fold faster. Association of apocytochrome c with cytochrome c heme lyase also takes place after solubilizing mitochondria with detergent. We conclude that the bound apocytochrome c, spanning the outer membrane, forms a complex with cytochrome c heme lyase from which it can react further to be converted to holocytochrome c and be translocated completely into the intermembrane space

Early steps in mitochondrial protein import

The process of insertion of precursor proteins into mitochondrial membranes was investigated using a hybrid protein (pSc1-c) that contains dual targeting information and, at the same time, membrane insertion activity. pSc1-c is composed of the matrix-targeting domain of the cytochrome c1 presequence joined to the amino terminus of apocytochrome c. It can be selectively imported along either a cytochrome c1 route into the mitochondrial matrix or via the cytochrome c route into the intermembrane space. In contrast to cytochrome c1, pSc1-c does not require the receptor system/GIP for entry into the matrix. The apocytochrome c in the pSc1-c fusion protein appears to exert its membrane insertion activity in such a manner that the matrix-targeting sequence gains direct access to the membrane potential-dependent step. These results attribute an essential function to the receptor system in facilitating the initial insertion of precursors into the mitochondrial membranes